This Project will contain all of my projects to practice in c. thats all mess rn ik ik lol. but it will be awesome when its done :).

1. C Fundamentals (001–026)

18. Command-Line Stopwatch & Timer Description: Start/stop stopwatch and countdown timer with lap support. Difficulty: Beginner Topics: time.h, signals, loops Estimated LOC: 160 Libraries: time.h, signal.h

19. Simple ASCII Table Explorer Description: Print ASCII codes and let users look up characters and ranges. Difficulty: Beginner Topics: char arithmetic, loops, formatting Estimated LOC: 90 Libraries: ctype.h

20. Quadratic & Polynomial Root Finder Description: Solve quadratics and evaluate polynomials at given points. Difficulty: Beginner Topics: math, floating point, discriminant Estimated LOC: 140 Libraries: math.h

21. Dice & Card Randomizer Description: Simulate dice rolls and shuffle/deal a standard card deck. Difficulty: Beginner Topics: random, arrays, Fisher-Yates Estimated LOC: 160 Libraries: stdlib.h, time.h

22. Simple Voting Tally System Description: Register candidates, cast votes, and print ranked results. Difficulty: Beginner Topics: structs, arrays, sorting Estimated LOC: 200 Libraries: stdio.h

23. Palindrome & Anagram Checker Description: Detect palindromes and test if two strings are anagrams. Difficulty: Beginner Topics: strings, counting, normalization Estimated LOC: 130 Libraries: ctype.h

24. Currency Formatter Description: Format raw amounts into localized currency strings with grouping. Difficulty: Beginner Topics: strings, integer math, formatting Estimated LOC: 140 Libraries: stdio.h

25. Simple State Machine Demo Description: Model a turnstile/traffic light as an explicit finite state machine. Difficulty: Beginner Topics: enums, switch, state transitions Estimated LOC: 150 Libraries: stdio.h

26. Command Argument Parser Mini-lib Description: Parse flags, options, and positional args like a tiny getopt. Difficulty: Beginner Topics: argv, strings, structs Estimated LOC: 220 Libraries: string.h

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2. Console Applications (027–048)

27. To-Do List Manager Description: Add, complete, delete, and persist tasks to a file. Difficulty: Beginner Topics: file I/O, structs, CRUD Estimated LOC: 300 Libraries: stdio.h

28. Contact Book / Address Manager Description: Store contacts with search, edit, and CSV export. Difficulty: Beginner Topics: structs, file I/O, search Estimated LOC: 350 Libraries: stdio.h

29. Expense Tracker Description: Log expenses by category and generate monthly summaries. Difficulty: Intermediate Topics: structs, file persistence, aggregation Estimated LOC: 400 Libraries: stdio.h, time.h

30. Inventory Management System Description: Track products, stock levels, and low-stock alerts. Difficulty: Intermediate Topics: CRUD, binary files, reporting Estimated LOC: 450 Libraries: stdio.h

31. Library Management System Description: Manage books, members, and borrow/return with due dates. Difficulty: Intermediate Topics: structs, file I/O, date logic Estimated LOC: 500 Libraries: time.h

32. Quiz Application with Question Bank Description: Load questions from a file, run timed quizzes, and score results. Difficulty: Intermediate Topics: file parsing, timing, scoring Estimated LOC: 400 Libraries: time.h

33. Personal Diary with Encryption Description: Journal entries encrypted with a passphrase at rest. Difficulty: Intermediate Topics: file I/O, XOR/AES, key handling Estimated LOC: 350 Libraries: stdlib.h

34. Command-Line Calendar Description: Print monthly/yearly calendars and highlight events. Difficulty: Intermediate Topics: date math, formatting, Zeller's congruence Estimated LOC: 300 Libraries: time.h

35. Habit Tracker with Streaks Description: Track daily habits and compute current/longest streaks. Difficulty: Intermediate Topics: date logic, persistence, stats Estimated LOC: 350 Libraries: time.h

36. Restaurant Billing System Description: Build orders from a menu and print an itemized bill with tax. Difficulty: Beginner Topics: structs, arithmetic, formatting Estimated LOC: 300 Libraries: stdio.h

37. Flashcard Spaced-Repetition Tool Description: Review flashcards using an SM-2 spaced-repetition schedule. Difficulty: Intermediate Topics: algorithms, persistence, date math Estimated LOC: 400 Libraries: time.h

38. Command-Line Password Manager Description: Store service credentials encrypted behind a master password. Difficulty: Advanced Topics: crypto, file I/O, KDF Estimated LOC: 500 Libraries: OpenSSL (libcrypto)

39. Movie / Media Catalog Description: Catalog media with ratings, tags, and multi-field search. Difficulty: Intermediate Topics: structs, search, sorting Estimated LOC: 400 Libraries: stdio.h

40. Command-Line Pomodoro Timer Description: Run focus/break cycles with notifications and session logs. Difficulty: Beginner Topics: timers, signals, logging Estimated LOC: 250 Libraries: time.h, signal.h

41. Employee Payroll System Description: Compute salaries, deductions, and generate payslips. Difficulty: Intermediate Topics: structs, arithmetic, reporting Estimated LOC: 450 Libraries: stdio.h

42. Ticket Booking System Description: Reserve seats on a grid, prevent double-booking, and persist. Difficulty: Intermediate Topics: 2D arrays, state, file I/O Estimated LOC: 450 Libraries: stdio.h

43. Command-Line Unit Test Runner Demo Description: Register test functions and run them with pass/fail reporting. Difficulty: Intermediate Topics: function pointers, macros, reporting Estimated LOC: 300 Libraries: stdio.h

44. Recipe Manager with Scaling Description: Store recipes and scale ingredient quantities by servings. Difficulty: Beginner Topics: structs, arithmetic, file I/O Estimated LOC: 350 Libraries: stdio.h

45. Command-Line Budget Envelope System Description: Allocate income into envelopes and track spending against them. Difficulty: Intermediate Topics: structs, persistence, aggregation Estimated LOC: 400 Libraries: stdio.h

46. Notes App with Full-Text Search Description: Store notes and search them with a simple inverted index. Difficulty: Advanced Topics: indexing, hashing, file I/O Estimated LOC: 550 Libraries: stdlib.h

47. Command-Line Chess Move Validator Description: Validate chess moves and detect check on a board state. Difficulty: Advanced Topics: 2D arrays, rules engine, logic Estimated LOC: 600 Libraries: stdio.h

48. Multi-User Auth Console Description: Register/login users with salted hashed passwords in a file. Difficulty: Intermediate Topics: hashing, file I/O, salts Estimated LOC: 400 Libraries: OpenSSL (libcrypto)

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3. Mathematics & Numerical Methods (049–075)

49. Arbitrary-Precision Integer (BigInt) Description: Add, subtract, multiply, and compare integers of unbounded size. Difficulty: Advanced Topics: arrays, carry propagation, algorithms Estimated LOC: 600 Libraries: stdlib.h

50. Rational Number Library Description: Exact fraction arithmetic with automatic reduction via GCD. Difficulty: Intermediate Topics: GCD, structs, normalization Estimated LOC: 300 Libraries: stdlib.h

51. Complex Number Library Description: Complex arithmetic including polar form and roots. Difficulty: Intermediate Topics: structs, trig, math Estimated LOC: 300 Libraries: math.h, complex.h

52. Matrix Algebra Library Description: Determinant, inverse, LU decomposition, and solving linear systems. Difficulty: Advanced Topics: linear algebra, numerical stability Estimated LOC: 700 Libraries: math.h

53. Numerical Integration Toolkit Description: Integrate functions via trapezoid, Simpson, and Gaussian quadrature. Difficulty: Intermediate Topics: numerical methods, function pointers Estimated LOC: 350 Libraries: math.h

54. Root-Finding Solver Description: Find roots via bisection, Newton-Raphson, and secant methods. Difficulty: Intermediate Topics: numerical methods, convergence Estimated LOC: 350 Libraries: math.h

55. ODE Solver (Runge-Kutta) Description: Solve ordinary differential equations with Euler and RK4. Difficulty: Advanced Topics: numerical methods, step control Estimated LOC: 400 Libraries: math.h

56. Fast Fourier Transform Description: Implement radix-2 Cooley-Tukey FFT and inverse FFT. Difficulty: Advanced Topics: DSP, recursion, complex numbers Estimated LOC: 400 Libraries: complex.h, math.h

57. Statistics Toolkit Description: Mean, variance, median, percentiles, correlation, and regression. Difficulty: Intermediate Topics: statistics, sorting, arrays Estimated LOC: 450 Libraries: math.h

58. Linear Regression Fitter Description: Fit lines and polynomials by least squares to a dataset. Difficulty: Intermediate Topics: linear algebra, statistics Estimated LOC: 350 Libraries: math.h

59. Prime Factorization & Pollard Rho Description: Factor large integers using trial division and Pollard's rho. Difficulty: Advanced Topics: number theory, algorithms Estimated LOC: 350 Libraries: stdlib.h

60. Modular Arithmetic Library Description: Modular exponentiation, inverse, and Chinese Remainder Theorem. Difficulty: Intermediate Topics: number theory, algorithms Estimated LOC: 300 Libraries: stdlib.h

61. Continued Fraction Calculator Description: Convert reals to continued fractions and back to rationals. Difficulty: Intermediate Topics: number theory, floating point Estimated LOC: 250 Libraries: math.h

62. Monte Carlo Pi & Integrator Description: Estimate pi and integrals via Monte Carlo sampling. Difficulty: Beginner Topics: random, statistics, convergence Estimated LOC: 200 Libraries: stdlib.h, math.h

63. Expression Evaluator (Shunting Yard) Description: Parse and evaluate infix math expressions with precedence. Difficulty: Intermediate Topics: stacks, parsing, algorithms Estimated LOC: 400 Libraries: stdlib.h

64. Symbolic Differentiation Engine Description: Differentiate symbolic expressions represented as trees. Difficulty: Advanced Topics: trees, recursion, parsing Estimated LOC: 600 Libraries: stdlib.h

65. Fixed-Point Arithmetic Library Description: Q-format fixed-point math for platforms without an FPU. Difficulty: Intermediate Topics: bit manipulation, scaling Estimated LOC: 350 Libraries: stdint.h

66. Vector & Quaternion Math Library Description: 3D vector, matrix, and quaternion ops for graphics/games. Difficulty: Intermediate Topics: linear algebra, 3D math Estimated LOC: 500 Libraries: math.h

67. Pseudo-Random Number Generators Description: Implement LCG, xorshift, and Mersenne Twister with quality tests. Difficulty: Intermediate Topics: PRNG, bit ops, statistics Estimated LOC: 400 Libraries: stdint.h

68. Numerical Base-N Calculator Description: Perform arithmetic in arbitrary bases with fractional support. Difficulty: Intermediate Topics: base conversion, strings Estimated LOC: 350 Libraries: stdlib.h

69. Combinatorics Toolkit Description: Compute permutations, combinations, and generate them lazily. Difficulty: Intermediate Topics: recursion, big numbers, generators Estimated LOC: 350 Libraries: stdlib.h

70. Geometric Primitives Library Description: Point/line/polygon intersection, convex hull, and area. Difficulty: Advanced Topics: computational geometry Estimated LOC: 550 Libraries: math.h

71. Calculator with Variables & Functions Description: A REPL calculator supporting assignment and user functions. Difficulty: Advanced Topics: parsing, symbol tables, eval Estimated LOC: 700 Libraries: stdlib.h

72. Interval Arithmetic Library Description: Track rounding error bounds by computing on intervals. Difficulty: Advanced Topics: floating point, numerical analysis Estimated LOC: 400 Libraries: math.h, fenv.h

73. Bignum Rational + Decimal Library Description: Arbitrary-precision decimal arithmetic with configurable precision. Difficulty: Advanced Topics: big integers, scaling, rounding Estimated LOC: 800 Libraries: stdlib.h

74. Newton Fractal / Mandelbrot Data Generator Description: Compute escape-time fractal data and export to PPM. Difficulty: Intermediate Topics: complex math, iteration, image output Estimated LOC: 300 Libraries: complex.h

75. Numerical Linear System Benchmark Description: Compare Gaussian elimination, Jacobi, and Gauss-Seidel solvers. Difficulty: Advanced Topics: numerical methods, benchmarking Estimated LOC: 500 Libraries: math.h, time.h

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4. Utilities (076–096)

76. wc Clone (word/line/byte count) Description: Count lines, words, characters, and bytes like coreutils wc. Difficulty: Beginner Topics: file I/O, streams, flags Estimated LOC: 200 Libraries: stdio.h

77. cat / tac Clone Description: Concatenate files to stdout, forward and reversed, with line numbers. Difficulty: Beginner Topics: file I/O, buffering Estimated LOC: 200 Libraries: stdio.h

78. head / tail with Follow Mode Description: Print first/last N lines and follow a growing file like tail -f. Difficulty: Intermediate Topics: file I/O, inotify/polling Estimated LOC: 300 Libraries: sys/inotify.h

79. grep Clone with Regex Description: Search files for lines matching a pattern with context flags. Difficulty: Intermediate Topics: regex, file I/O, flags Estimated LOC: 400 Libraries: regex.h

80. find Clone Description: Recursively find files by name, type, size, and modification time. Difficulty: Intermediate Topics: directory traversal, filtering Estimated LOC: 400 Libraries: dirent.h, sys/stat.h

81. ls Clone with Colors Description: List directory contents with long format, sorting, and colors. Difficulty: Intermediate Topics: stat, permissions, formatting Estimated LOC: 450 Libraries: dirent.h, sys/stat.h

82. du Disk Usage Analyzer Description: Compute directory sizes recursively with a human-readable tree. Difficulty: Intermediate Topics: recursion, stat, formatting Estimated LOC: 350 Libraries: dirent.h

83. diff Tool (LCS-based) Description: Show line differences between two files using longest common subsequence. Difficulty: Advanced Topics: dynamic programming, file I/O Estimated LOC: 450 Libraries: stdlib.h

84. sort Clone Description: Sort lines with numeric, reverse, unique, and key options. Difficulty: Intermediate Topics: sorting, comparators, flags Estimated LOC: 350 Libraries: stdlib.h

85. uniq Clone Description: Filter or count adjacent duplicate lines with flag options. Difficulty: Beginner Topics: streams, string compare Estimated LOC: 200 Libraries: stdio.h

86. xxd / Hex Dump Utility Description: Dump files as hex + ASCII and reverse a hex dump to binary. Difficulty: Intermediate Topics: binary I/O, formatting Estimated LOC: 300 Libraries: stdio.h

87. File Splitter & Joiner (split) Description: Split large files into chunks and reassemble them exactly. Difficulty: Beginner Topics: binary I/O, buffering Estimated LOC: 250 Libraries: stdio.h

88. Duplicate File Finder Description: Find duplicate files by size then content hash. Difficulty: Intermediate Topics: hashing, hash tables, traversal Estimated LOC: 400 Libraries: OpenSSL (libcrypto)

89. Batch File Renamer Description: Rename files in bulk with patterns, counters, and dry-run mode. Difficulty: Intermediate Topics: strings, directory ops Estimated LOC: 350 Libraries: dirent.h

90. tree Directory Visualizer Description: Print a directory hierarchy as an ASCII/Unicode tree. Difficulty: Intermediate Topics: recursion, formatting Estimated LOC: 300 Libraries: dirent.h

91. env / Environment Inspector Description: Print, filter, and run commands with modified environment variables. Difficulty: Beginner Topics: environ, exec, strings Estimated LOC: 200 Libraries: unistd.h

92. Clipboard Manager (X11/Wayland-agnostic file-backed) Description: Store and recall multiple clipboard entries from the CLI. Difficulty: Intermediate Topics: file I/O, IPC, history Estimated LOC: 350 Libraries: stdio.h

93. watch Command Clone Description: Re-run a command on an interval and display refreshing output. Difficulty: Intermediate Topics: fork/exec, terminal control, timing Estimated LOC: 300 Libraries: unistd.h

94. QR Code / Barcode Data Encoder Description: Encode text into a QR matrix and render it as terminal blocks. Difficulty: Advanced Topics: Reed-Solomon, bit packing Estimated LOC: 800 Libraries: none

95. cron-style Task Scheduler Description: Parse crontab syntax and run scheduled commands. Difficulty: Advanced Topics: parsing, time, fork/exec Estimated LOC: 500 Libraries: unistd.h, time.h

96. Progress Bar & Spinner Library Description: Reusable animated progress bars and spinners for CLI tools. Difficulty: Beginner Topics: terminal control, timing Estimated LOC: 250 Libraries: unistd.h

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5. File Processing (097–116)

97. CSV Parser & Query Tool Description: Parse RFC-4180 CSV and run simple column filters and projections. Difficulty: Intermediate Topics: parsing, quoting, state machine Estimated LOC: 450 Libraries: stdio.h

98. INI Configuration Parser Description: Read and write INI files with sections, comments, and types. Difficulty: Beginner Topics: parsing, hash maps Estimated LOC: 300 Libraries: stdio.h

99. JSON Parser & Serializer Description: Parse JSON into a value tree and serialize it back. Difficulty: Advanced Topics: recursive descent, memory, unicode Estimated LOC: 700 Libraries: stdlib.h

100. Binary File Format Reader (BMP) Description: Parse and manipulate BMP headers and pixel data. Difficulty: Intermediate Topics: binary layout, structs, endianness Estimated LOC: 350 Libraries: stdint.h

101. WAV Audio File Reader/Writer Description: Read, generate, and modify PCM WAV files. Difficulty: Intermediate Topics: RIFF format, binary I/O Estimated LOC: 400 Libraries: stdint.h

102. Tarball Creator & Extractor Description: Build and unpack POSIX tar archives without external libs. Difficulty: Advanced Topics: archive format, checksums Estimated LOC: 600 Libraries: sys/stat.h

103. File Metadata Extractor Description: Report size, timestamps, permissions, and MIME guess for files. Difficulty: Beginner Topics: stat, magic bytes Estimated LOC: 300 Libraries: sys/stat.h

104. Log File Rotator Description: Rotate, compress, and prune log files by size or age. Difficulty: Intermediate Topics: file ops, compression, scheduling Estimated LOC: 400 Libraries: zlib

105. EXIF Metadata Reader Description: Extract camera metadata from JPEG EXIF segments. Difficulty: Advanced Topics: TIFF/EXIF layout, endianness Estimated LOC: 550 Libraries: stdint.h

106. Memory-Mapped File Text Search Description: Search huge files fast using mmap instead of read loops. Difficulty: Intermediate Topics: mmap, string search Estimated LOC: 300 Libraries: sys/mman.h

107. File Integrity Monitor Description: Track file hashes and alert on unexpected changes. Difficulty: Intermediate Topics: hashing, persistence, traversal Estimated LOC: 400 Libraries: OpenSSL (libcrypto)

108. Fixed-Width Record Parser Description: Parse and reformat fixed-width column data files. Difficulty: Beginner Topics: parsing, formatting Estimated LOC: 250 Libraries: stdio.h

109. PDF Text Extractor (basic) Description: Extract uncompressed text streams from simple PDF files. Difficulty: Advanced Topics: PDF structure, tokenizing Estimated LOC: 700 Libraries: zlib

110. ELF Header Parser Description: Parse ELF headers, sections, and symbol tables. Difficulty: Advanced Topics: ELF format, binary layout Estimated LOC: 500 Libraries: elf.h

111. Sqlite-Style Page File Reader Description: Read the on-disk pages of a SQLite database file. Difficulty: Advanced Topics: file format, B-trees, endianness Estimated LOC: 600 Libraries: stdint.h

112. Config File Diff & Merge Description: Compare two config files and produce a merged result. Difficulty: Intermediate Topics: parsing, diffing Estimated LOC: 400 Libraries: stdio.h

113. Recursive File Encryptor Description: Encrypt/decrypt entire directory trees with a password. Difficulty: Advanced Topics: crypto, traversal, streaming Estimated LOC: 500 Libraries: OpenSSL (libcrypto)

114. File Type Identifier (file clone) Description: Identify file types by magic-number signatures. Difficulty: Intermediate Topics: magic bytes, tables Estimated LOC: 400 Libraries: stdio.h

115. Line-Ending Normalizer Description: Convert between CRLF/LF/CR and detect mixed endings. Difficulty: Beginner Topics: byte scanning, I/O Estimated LOC: 200 Libraries: stdio.h

116. Streaming File Deduplicator Description: Deduplicate a byte stream into content-addressed blocks. Difficulty: Advanced Topics: rolling hash, chunking Estimated LOC: 500 Libraries: stdlib.h

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6. Text Processing (117–137)

117. sed-style Stream Editor (subset) Description: Apply substitution, delete, and print commands to a stream. Difficulty: Advanced Topics: parsing, regex, streams Estimated LOC: 600 Libraries: regex.h

118. awk-style Field Processor (subset) Description: Run per-line field programs with patterns and actions. Difficulty: Advanced Topics: parsing, expression eval Estimated LOC: 800 Libraries: stdlib.h

119. Markdown to HTML Converter Description: Convert core Markdown syntax to valid HTML. Difficulty: Intermediate Topics: parsing, state machine, output Estimated LOC: 600 Libraries: stdio.h

120. Word Frequency Counter Description: Tokenize text and rank words by frequency. Difficulty: Beginner Topics: hashing, sorting, tokenizing Estimated LOC: 300 Libraries: stdlib.h

121. Spell Checker with Suggestions Description: Flag misspellings and suggest edits by edit distance. Difficulty: Advanced Topics: dictionaries, dynamic programming Estimated LOC: 550 Libraries: stdlib.h

122. Regex Engine (NFA/backtracking) Description: Implement a small regex engine supporting . * + ? | (). Difficulty: Advanced Topics: automata, recursion, parsing Estimated LOC: 700 Libraries: stdlib.h

123. Text Justifier & Wrapper Description: Reflow paragraphs to a width with greedy or optimal wrapping. Difficulty: Intermediate Topics: dynamic programming, strings Estimated LOC: 400 Libraries: stdio.h

124. Template Engine Description: Render templates with variable substitution, loops, and conditionals. Difficulty: Advanced Topics: parsing, symbol tables Estimated LOC: 650 Libraries: stdlib.h

125. Syntax Highlighter (terminal) Description: Tokenize source code and colorize keywords in the terminal. Difficulty: Intermediate Topics: lexing, ANSI colors Estimated LOC: 450 Libraries: stdio.h

126. Levenshtein / Fuzzy String Matcher Description: Rank candidate strings by fuzzy similarity to a query. Difficulty: Intermediate Topics: dynamic programming, scoring Estimated LOC: 300 Libraries: stdlib.h

127. Text Adventure Story Parser Description: Parse a branching-story file format into a playable graph. Difficulty: Intermediate Topics: parsing, graphs, state Estimated LOC: 450 Libraries: stdlib.h

128. ROT13 / Caesar / Vigenère Toolkit Description: Encode/decode classic substitution ciphers with cracking hints. Difficulty: Beginner Topics: strings, modular arithmetic Estimated LOC: 300 Libraries: ctype.h

129. UTF-8 Encoder/Decoder & Validator Description: Decode, validate, and re-encode UTF-8 byte streams. Difficulty: Intermediate Topics: unicode, bit manipulation Estimated LOC: 350 Libraries: stdint.h

130. Text Statistics & Readability Scorer Description: Compute Flesch-Kincaid and other readability metrics. Difficulty: Intermediate Topics: tokenizing, statistics Estimated LOC: 350 Libraries: stdio.h

131. Autocomplete Engine (Trie-based) Description: Suggest completions from a prefix using a trie. Difficulty: Intermediate Topics: tries, recursion Estimated LOC: 400 Libraries: stdlib.h

132. Diff-based Merge Conflict Resolver Description: Perform three-way merges and mark conflicts. Difficulty: Advanced Topics: diff algorithms, merging Estimated LOC: 600 Libraries: stdlib.h

133. CSV/TSV to Markdown Table Converter Description: Convert delimited data into aligned Markdown tables. Difficulty: Beginner Topics: parsing, formatting Estimated LOC: 250 Libraries: stdio.h

134. Text Compression Visualizer Description: Show how Huffman/RLE compresses a given text sample. Difficulty: Intermediate Topics: compression, trees, visualization Estimated LOC: 450 Libraries: stdlib.h

135. Named-Entity Tokenizer Description: Tokenize text into words, numbers, emails, and URLs by rules. Difficulty: Intermediate Topics: lexing, state machines Estimated LOC: 400 Libraries: ctype.h

136. Boyer-Moore / KMP Search Tool Description: Fast substring search implementing Boyer-Moore and KMP. Difficulty: Advanced Topics: string algorithms Estimated LOC: 350 Libraries: stdlib.h

137. Text Table Formatter (pretty-print) Description: Auto-size columns and render bordered ASCII tables. Difficulty: Intermediate Topics: formatting, measurement Estimated LOC: 350 Libraries: stdio.h

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7. Data Structures (138–164)

138. Dynamic Array (Vector) Description: Generic growable array with amortized O(1) append. Difficulty: Beginner Topics: realloc, generics via void*, macros Estimated LOC: 250 Libraries: stdlib.h

139. Singly & Doubly Linked Lists Description: Full linked-list library with insert, delete, reverse, and sort. Difficulty: Beginner Topics: pointers, memory Estimated LOC: 350 Libraries: stdlib.h

140. Stack & Queue Library Description: Array- and list-backed stacks, queues, and deques. Difficulty: Beginner Topics: abstract data types Estimated LOC: 300 Libraries: stdlib.h

141. Hash Table (open addressing + chaining) Description: Generic hash map with two collision strategies and resizing. Difficulty: Intermediate Topics: hashing, load factor, memory Estimated LOC: 450 Libraries: stdlib.h

142. Binary Search Tree Description: BST with insert, delete, traversal, and balance checks. Difficulty: Intermediate Topics: trees, recursion Estimated LOC: 400 Libraries: stdlib.h

143. AVL Tree Description: Self-balancing BST with rotation-based rebalancing. Difficulty: Advanced Topics: balanced trees, rotations Estimated LOC: 500 Libraries: stdlib.h

144. Red-Black Tree Description: Red-black tree with full insert/delete rebalancing. Difficulty: Advanced Topics: balanced trees, invariants Estimated LOC: 700 Libraries: stdlib.h

145. B-Tree / B+Tree Description: Disk-friendly B-tree supporting range scans. Difficulty: Advanced Topics: multiway trees, paging Estimated LOC: 800 Libraries: stdlib.h

146. Binary Heap & Priority Queue Description: Min/max heap with heapify and a priority queue API. Difficulty: Intermediate Topics: heaps, arrays Estimated LOC: 300 Libraries: stdlib.h

147. Fibonacci / Pairing Heap Description: Advanced heap with fast decrease-key for Dijkstra. Difficulty: Advanced Topics: amortized analysis, heaps Estimated LOC: 550 Libraries: stdlib.h

148. Trie & Radix Tree Description: Prefix tree and compressed radix tree for string keys. Difficulty: Intermediate Topics: tries, string keys Estimated LOC: 450 Libraries: stdlib.h

149. Graph Library (adjacency list/matrix) Description: Represent graphs and run BFS/DFS with both representations. Difficulty: Intermediate Topics: graphs, traversal Estimated LOC: 450 Libraries: stdlib.h

150. Disjoint Set (Union-Find) Description: Union-find with path compression and union by rank. Difficulty: Intermediate Topics: amortized analysis Estimated LOC: 200 Libraries: stdlib.h

151. Skip List Description: Probabilistic ordered set with O(log n) search. Difficulty: Advanced Topics: randomization, linked structures Estimated LOC: 450 Libraries: stdlib.h

152. Bloom Filter Description: Space-efficient probabilistic membership test. Difficulty: Intermediate Topics: hashing, bit arrays Estimated LOC: 300 Libraries: stdlib.h

153. LRU Cache Description: Fixed-size cache with O(1) get/put via hashmap + list. Difficulty: Intermediate Topics: hashing, linked lists Estimated LOC: 350 Libraries: stdlib.h

154. Circular Ring Buffer Description: Lock-free-friendly ring buffer for producer/consumer data. Difficulty: Intermediate Topics: buffers, modular indexing Estimated LOC: 250 Libraries: stdlib.h

155. Segment Tree Description: Range query/update structure for sums, mins, and maxes. Difficulty: Advanced Topics: divide and conquer, lazy propagation Estimated LOC: 450 Libraries: stdlib.h

156. Fenwick Tree (BIT) Description: Binary indexed tree for prefix sums with updates. Difficulty: Intermediate Topics: bit manipulation, prefix sums Estimated LOC: 200 Libraries: stdlib.h

157. Suffix Array & LCP Description: Build suffix arrays for fast substring queries. Difficulty: Advanced Topics: string algorithms, sorting Estimated LOC: 500 Libraries: stdlib.h

158. Suffix Tree (Ukkonen) Description: Linear-time suffix tree construction for pattern matching. Difficulty: Advanced Topics: string algorithms, trees Estimated LOC: 700 Libraries: stdlib.h

159. Quadtree / Octree Description: Spatial partition tree for 2D/3D point queries. Difficulty: Advanced Topics: spatial indexing, recursion Estimated LOC: 550 Libraries: stdlib.h

160. K-D Tree Description: Multidimensional tree for nearest-neighbor search. Difficulty: Advanced Topics: spatial data, recursion Estimated LOC: 500 Libraries: stdlib.h

161. Generic Iterator Framework Description: Uniform iteration interface over multiple container types. Difficulty: Intermediate Topics: function pointers, abstraction Estimated LOC: 350 Libraries: stdlib.h

162. Persistent (Immutable) Data Structures Description: Structural-sharing immutable list and map. Difficulty: Advanced Topics: persistence, reference counting Estimated LOC: 600 Libraries: stdlib.h

163. Rope (heavy text buffer) Description: Rope structure for efficient large-string editing. Difficulty: Advanced Topics: balanced trees, strings Estimated LOC: 600 Libraries: stdlib.h

164. Interval Tree Description: Store intervals and query all that overlap a point/range. Difficulty: Advanced Topics: augmented trees Estimated LOC: 450 Libraries: stdlib.h

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8. Algorithms (165–197)

165. Sorting Algorithms Visual Suite Description: Implement and benchmark 10+ sorting algorithms with stats. Difficulty: Intermediate Topics: sorting, benchmarking Estimated LOC: 600 Libraries: time.h

166. Search Algorithms Toolkit Description: Linear, binary, interpolation, and exponential search. Difficulty: Beginner Topics: searching, complexity Estimated LOC: 300 Libraries: stdlib.h

167. Dijkstra Shortest Path Description: Compute shortest paths with a priority-queue Dijkstra. Difficulty: Intermediate Topics: graphs, heaps Estimated LOC: 350 Libraries: stdlib.h

168. A* Pathfinding Description: Grid pathfinding with heuristics and obstacle maps. Difficulty: Intermediate Topics: graphs, heuristics Estimated LOC: 400 Libraries: stdlib.h

169. Bellman-Ford & Negative Cycles Description: Shortest paths allowing negative edges with cycle detection. Difficulty: Intermediate Topics: graphs, relaxation Estimated LOC: 300 Libraries: stdlib.h

170. Floyd-Warshall All-Pairs Description: Compute all-pairs shortest paths via dynamic programming. Difficulty: Intermediate Topics: dynamic programming, graphs Estimated LOC: 250 Libraries: stdlib.h

171. Minimum Spanning Tree (Kruskal & Prim) Description: Build MSTs with union-find and priority queues. Difficulty: Intermediate Topics: graphs, greedy Estimated LOC: 400 Libraries: stdlib.h

172. Topological Sort & Cycle Detection Description: Order a DAG and detect cycles in dependencies. Difficulty: Intermediate Topics: graphs, DFS Estimated LOC: 300 Libraries: stdlib.h

173. Strongly Connected Components (Tarjan) Description: Find SCCs in a directed graph in linear time. Difficulty: Advanced Topics: graphs, DFS Estimated LOC: 350 Libraries: stdlib.h

174. Max Flow (Edmonds-Karp / Dinic) Description: Compute maximum flow and minimum cut in networks. Difficulty: Advanced Topics: graphs, flow Estimated LOC: 500 Libraries: stdlib.h

175. Dynamic Programming Problem Set Solver Description: Solve knapsack, LIS, edit distance, and coin change generically. Difficulty: Intermediate Topics: dynamic programming Estimated LOC: 500 Libraries: stdlib.h

176. Backtracking Solver Framework Description: Generic backtracking engine for N-Queens, Sudoku, and mazes. Difficulty: Intermediate Topics: recursion, pruning Estimated LOC: 500 Libraries: stdlib.h

177. String Matching Suite Description: KMP, Rabin-Karp, Boyer-Moore, and Aho-Corasick in one lib. Difficulty: Advanced Topics: string algorithms Estimated LOC: 700 Libraries: stdlib.h

178. Convex Hull Algorithms Description: Compute hulls via Graham scan and Andrew's monotone chain. Difficulty: Advanced Topics: computational geometry Estimated LOC: 400 Libraries: math.h

179. Line-Segment Intersection Sweep Description: Find all intersections with a Bentley-Ottmann sweep line. Difficulty: Advanced Topics: computational geometry, events Estimated LOC: 550 Libraries: stdlib.h

180. Huffman Coding Description: Build Huffman trees to compress and decompress data. Difficulty: Intermediate Topics: greedy, trees, bit I/O Estimated LOC: 450 Libraries: stdlib.h

181. Simplex Linear Programming Solver Description: Solve LP problems with the simplex method. Difficulty: Advanced Topics: optimization, linear algebra Estimated LOC: 600 Libraries: math.h

182. Genetic Algorithm Framework Description: Evolve solutions with selection, crossover, and mutation. Difficulty: Advanced Topics: metaheuristics, randomness Estimated LOC: 500 Libraries: stdlib.h

183. Simulated Annealing Optimizer Description: Optimize hard problems (TSP) with annealing schedules. Difficulty: Advanced Topics: metaheuristics, probability Estimated LOC: 450 Libraries: math.h

184. Traveling Salesman Approximations Description: Solve TSP with nearest-neighbor, 2-opt, and Christofides-style heuristics. Difficulty: Advanced Topics: optimization, graphs Estimated LOC: 550 Libraries: math.h

185. Reservoir Sampling & Streaming Stats Description: Sample and summarize data from unbounded streams. Difficulty: Intermediate Topics: probability, streaming Estimated LOC: 300 Libraries: stdlib.h

186. HyperLogLog Cardinality Estimator Description: Estimate distinct counts in huge streams with tiny memory. Difficulty: Advanced Topics: hashing, probabilistic counting Estimated LOC: 400 Libraries: stdlib.h

187. Rabin-Karp Plagiarism Detector Description: Detect copied passages between documents via rolling hashes. Difficulty: Intermediate Topics: hashing, string algorithms Estimated LOC: 400 Libraries: stdlib.h

188. Union of Rectangles / Sweep Area Description: Compute total covered area of overlapping rectangles. Difficulty: Advanced Topics: sweep line, segment trees Estimated LOC: 500 Libraries: stdlib.h

189. Matrix Chain & DP Optimizer Description: Find optimal parenthesization for matrix multiplication. Difficulty: Intermediate Topics: dynamic programming Estimated LOC: 250 Libraries: stdlib.h

190. Fast Exponentiation & Matrix Power Description: Compute large powers and linear recurrences fast. Difficulty: Intermediate Topics: divide and conquer Estimated LOC: 250 Libraries: stdlib.h

191. Miller-Rabin Primality Test Description: Probabilistic primality testing for large integers. Difficulty: Advanced Topics: number theory, modular math Estimated LOC: 300 Libraries: stdint.h

192. Karatsuba & FFT Multiplication Description: Multiply large numbers faster than schoolbook methods. Difficulty: Advanced Topics: divide and conquer, FFT Estimated LOC: 500 Libraries: complex.h

193. Job Scheduling Algorithms Description: Compare FCFS, SJF, and interval scheduling optimality. Difficulty: Intermediate Topics: greedy, scheduling Estimated LOC: 350 Libraries: stdlib.h

194. Approximate Nearest Neighbor (LSH) Description: Find similar high-dimensional vectors with locality-sensitive hashing. Difficulty: Advanced Topics: hashing, vectors Estimated LOC: 500 Libraries: math.h

195. Boyer-Moore Majority & Streaming Heavy Hitters Description: Find frequent elements in a stream in one pass. Difficulty: Intermediate Topics: streaming, counting Estimated LOC: 250 Libraries: stdlib.h

196. Maze Generation Algorithms Description: Generate mazes via DFS, Prim, and recursive division. Difficulty: Intermediate Topics: graphs, randomness Estimated LOC: 400 Libraries: stdlib.h

197. Algorithm Complexity Profiler Description: Empirically fit runtime curves to infer Big-O of a function. Difficulty: Advanced Topics: benchmarking, curve fitting Estimated LOC: 400 Libraries: time.h, math.h

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9. Games (198–224)

198. Tic-Tac-Toe with Minimax AI Description: Unbeatable tic-tac-toe using the minimax algorithm. Difficulty: Beginner Topics: game trees, recursion Estimated LOC: 300 Libraries: stdio.h

199. Hangman Description: Word-guessing game with categories and ASCII gallows. Difficulty: Beginner Topics: strings, state Estimated LOC: 250 Libraries: stdio.h

200. Connect Four with AI Description: Two-player Connect Four with an alpha-beta AI opponent. Difficulty: Intermediate Topics: game trees, alpha-beta Estimated LOC: 450 Libraries: stdio.h

201. Snake (terminal) Description: Classic snake with growing tail and collision detection. Difficulty: Intermediate Topics: game loop, input, ncurses Estimated LOC: 350 Libraries: ncurses

202. Tetris (terminal) Description: Falling-block puzzle with rotation, line clears, and scoring. Difficulty: Advanced Topics: game loop, collision, rotation Estimated LOC: 600 Libraries: ncurses

203. 2048 Description: Sliding-tile number-merging game with animations. Difficulty: Intermediate Topics: grids, input, merging Estimated LOC: 400 Libraries: ncurses

204. Minesweeper Description: Grid minesweeper with flood-fill reveal and flagging. Difficulty: Intermediate Topics: recursion, grids Estimated LOC: 450 Libraries: ncurses

205. Sudoku Generator & Solver Description: Generate valid puzzles and solve them by backtracking. Difficulty: Intermediate Topics: backtracking, constraints Estimated LOC: 500 Libraries: stdio.h

206. Text-Based RPG Engine Description: Data-driven RPG with rooms, items, combat, and saves. Difficulty: Advanced Topics: state machines, parsing, persistence Estimated LOC: 900 Libraries: stdlib.h

207. Blackjack Description: Card game with dealer AI, betting, and basic strategy hints. Difficulty: Intermediate Topics: cards, probability, state Estimated LOC: 450 Libraries: stdlib.h

208. Checkers with AI Description: Full checkers with forced captures and minimax AI. Difficulty: Advanced Topics: board games, game trees Estimated LOC: 700 Libraries: stdio.h

209. Chess Engine (basic) Description: Legal-move chess with a simple evaluation and search. Difficulty: Advanced Topics: board representation, search Estimated LOC: 1500 Libraries: stdio.h

210. Pong (SDL2) Description: Two-paddle Pong with physics and score. Difficulty: Intermediate Topics: game loop, collision, rendering Estimated LOC: 400 Libraries: SDL2

211. Breakout / Arkanoid (SDL2) Description: Brick-breaking game with power-ups and levels. Difficulty: Intermediate Topics: physics, collision, levels Estimated LOC: 600 Libraries: SDL2

212. Space Invaders (Raylib) Description: Wave-based shooter with enemies, bullets, and score. Difficulty: Intermediate Topics: game loop, entities Estimated LOC: 600 Libraries: Raylib

213. Flappy Bird Clone (Raylib) Description: One-button flappy game with procedural pipes. Difficulty: Beginner Topics: physics, collision Estimated LOC: 350 Libraries: Raylib

214. Platformer with Tile Maps (SDL2) Description: Side-scroller with tile collision, gravity, and camera. Difficulty: Advanced Topics: physics, tilemaps, camera Estimated LOC: 1000 Libraries: SDL2

215. Roguelike Dungeon Crawler Description: Procedural dungeons, turn-based combat, and permadeath. Difficulty: Advanced Topics: procedural generation, FOV Estimated LOC: 1200 Libraries: ncurses

216. Conway's Game of Life Description: Cellular automaton with patterns, wrap, and speed control. Difficulty: Beginner Topics: grids, simulation Estimated LOC: 300 Libraries: ncurses

217. Wordle Clone Description: Daily word puzzle with color feedback and stats. Difficulty: Beginner Topics: strings, feedback logic Estimated LOC: 300 Libraries: stdio.h

218. Simon Says Memory Game Description: Sequence-memory game with increasing difficulty and sound. Difficulty: Beginner Topics: sequences, timing Estimated LOC: 300 Libraries: ncurses

219. Reversi / Othello with AI Description: Othello with legal-move highlighting and heuristic AI. Difficulty: Advanced Topics: board games, evaluation Estimated LOC: 600 Libraries: stdio.h

220. Asteroids (Raylib) Description: Vector-style shooter with wrapping physics and splitting rocks. Difficulty: Intermediate Topics: vector math, physics Estimated LOC: 700 Libraries: Raylib

221. Tower Defense (SDL2) Description: Place towers to stop waves along a path with economy. Difficulty: Advanced Topics: pathfinding, entities, balancing Estimated LOC: 1200 Libraries: SDL2

222. Card Game Framework (rules engine) Description: Configurable engine to implement multiple card games. Difficulty: Advanced Topics: rules engines, abstraction Estimated LOC: 900 Libraries: stdlib.h

223. Physics Sandbox (Verlet) Description: Simulate ropes, cloth, and collisions with Verlet integration. Difficulty: Advanced Topics: physics, integration Estimated LOC: 700 Libraries: Raylib

224. Multiplayer Terminal Snake (networked) Description: Two-player snake over TCP with a shared game state. Difficulty: Advanced Topics: networking, game state sync Estimated LOC: 800 Libraries: ncurses, sockets

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10. Operating Systems (225–245)

225. Bootloader (x86 real mode) Description: Write a 512-byte MBR bootloader that prints to screen. Difficulty: Advanced Topics: assembly, BIOS, boot Estimated LOC: 300 Libraries: NASM + C

226. Minimal Kernel ("Hello Kernel") Description: Boot into a C kernel that writes to VGA text memory. Difficulty: Advanced Topics: freestanding C, linker scripts Estimated LOC: 500 Libraries: none (freestanding)

227. Physical Memory Manager (frame allocator) Description: Manage physical frames with a bitmap allocator in a kernel. Difficulty: Advanced Topics: memory management, bitmaps Estimated LOC: 500 Libraries: none (freestanding)

228. Virtual Memory & Paging Description: Set up page tables and enable paging in a hobby kernel. Difficulty: Advanced Topics: paging, MMU Estimated LOC: 700 Libraries: none (freestanding)

229. Interrupt Descriptor Table & Handlers Description: Install IDT entries and handle keyboard/timer interrupts. Difficulty: Advanced Topics: interrupts, ISRs Estimated LOC: 600 Libraries: none (freestanding)

230. Cooperative Multitasking Scheduler Description: Switch between kernel tasks using saved contexts. Difficulty: Advanced Topics: context switching, scheduling Estimated LOC: 600 Libraries: none (freestanding)

231. Preemptive Round-Robin Scheduler Description: Timer-driven preemptive scheduling of processes. Difficulty: Advanced Topics: scheduling, timers Estimated LOC: 700 Libraries: none (freestanding)

232. Simple In-Memory Filesystem Description: Implement a RAM filesystem with files, dirs, and a VFS layer. Difficulty: Advanced Topics: filesystems, data structures Estimated LOC: 800 Libraries: none (freestanding)

233. FAT12/16 Filesystem Reader Description: Read files from a FAT-formatted disk image. Difficulty: Advanced Topics: filesystems, on-disk layout Estimated LOC: 700 Libraries: stdio.h

234. Userspace Threading Library (ucontext) Description: Implement green threads with your own scheduler. Difficulty: Advanced Topics: context switching, coroutines Estimated LOC: 500 Libraries: ucontext.h

235. Slab / Buddy Kernel Allocator Description: Implement buddy and slab allocators for kernel memory. Difficulty: Advanced Topics: allocators, fragmentation Estimated LOC: 700 Libraries: none (freestanding)

236. System Call Interface Demo Description: Add a syscall gate and expose a few kernel services to userspace. Difficulty: Advanced Topics: syscalls, privilege levels Estimated LOC: 600 Libraries: none (freestanding)

237. ELF Program Loader Description: Load and execute a static ELF binary in a hobby OS. Difficulty: Advanced Topics: ELF, loaders, memory Estimated LOC: 700 Libraries: elf.h

238. Process Simulator with Scheduling Policies Description: Simulate FCFS/SJF/RR/priority scheduling and report metrics. Difficulty: Intermediate Topics: scheduling, simulation Estimated LOC: 500 Libraries: stdlib.h

239. Deadlock Detection Simulator Description: Model resource allocation and detect deadlock cycles. Difficulty: Intermediate Topics: graphs, banker's algorithm Estimated LOC: 450 Libraries: stdlib.h

240. Page Replacement Simulator Description: Compare FIFO, LRU, Optimal, and Clock page replacement. Difficulty: Intermediate Topics: memory management, simulation Estimated LOC: 450 Libraries: stdlib.h

241. Disk Scheduling Simulator Description: Simulate FCFS, SSTF, SCAN, and C-SCAN disk head movement. Difficulty: Intermediate Topics: scheduling, simulation Estimated LOC: 400 Libraries: stdlib.h

242. Semaphore & Mutex Primitives (from scratch) Description: Build synchronization primitives on atomics/futex. Difficulty: Advanced Topics: concurrency, atomics Estimated LOC: 400 Libraries: pthread, atomics

243. Producer-Consumer & Dining Philosophers Description: Classic concurrency problems with visible state. Difficulty: Intermediate Topics: synchronization, threads Estimated LOC: 400 Libraries: pthread

244. Shell with Job Control Description: A kernel-adjacent userspace shell supporting fg/bg jobs. Difficulty: Advanced Topics: process groups, signals Estimated LOC: 800 Libraries: unistd.h, signal.h

245. Boot-to-REPL Mini OS Description: Boot into a tiny interactive command shell in your kernel. Difficulty: Advanced Topics: kernel, keyboard, parsing Estimated LOC: 1000 Libraries: none (freestanding)

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11. Linux & System Programming (246–270)

246. ps Process Lister Description: List running processes by parsing /proc. Difficulty: Intermediate Topics: /proc, parsing Estimated LOC: 350 Libraries: dirent.h

247. top-style System Monitor Description: Live CPU, memory, and process view refreshing in the terminal. Difficulty: Advanced Topics: /proc, ncurses, stats Estimated LOC: 700 Libraries: ncurses

248. strace-lite Syscall Tracer Description: Trace a child process's syscalls using ptrace. Difficulty: Advanced Topics: ptrace, syscalls Estimated LOC: 600 Libraries: sys/ptrace.h

249. kill / Signal Sender Description: Send signals to processes and demonstrate handlers. Difficulty: Beginner Topics: signals, pid Estimated LOC: 200 Libraries: signal.h

250. Daemonizer Description: Turn a program into a well-behaved background daemon. Difficulty: Intermediate Topics: fork, setsid, file descriptors Estimated LOC: 300 Libraries: unistd.h

251. Inter-Process Pipe Chat Description: Two processes chatting over named pipes (FIFOs). Difficulty: Intermediate Topics: FIFOs, IPC Estimated LOC: 300 Libraries: sys/stat.h

252. Shared Memory + Semaphore IPC Description: Share a data structure between processes via SysV/POSIX shm. Difficulty: Advanced Topics: shared memory, sync Estimated LOC: 400 Libraries: sys/shm.h, semaphore.h

253. Message Queue IPC Demo Description: Pass structured messages between processes via message queues. Difficulty: Intermediate Topics: IPC, message queues Estimated LOC: 350 Libraries: mqueue.h

254. File Watcher (inotify) Description: React to filesystem create/modify/delete events. Difficulty: Intermediate Topics: inotify, events Estimated LOC: 350 Libraries: sys/inotify.h

255. Memory Usage Profiler for a PID Description: Report RSS, heap, and mappings for a process from /proc. Difficulty: Intermediate Topics: /proc/maps, parsing Estimated LOC: 400 Libraries: stdio.h

256. nice/Priority Manager Description: Adjust process scheduling priorities and affinity. Difficulty: Intermediate Topics: scheduling, syscalls Estimated LOC: 250 Libraries: sched.h

257. epoll-based Event Loop Library Description: Reusable event loop for readable/writable fd callbacks. Difficulty: Advanced Topics: epoll, event-driven design Estimated LOC: 500 Libraries: sys/epoll.h

258. Zombie Reaper & Process Supervisor Description: Supervise child processes and restart them on crash. Difficulty: Intermediate Topics: fork, wait, signals Estimated LOC: 400 Libraries: sys/wait.h

259. mount/Filesystem Info Tool Description: Report mounted filesystems and usage from /proc/mounts + statvfs. Difficulty: Intermediate Topics: statvfs, parsing Estimated LOC: 300 Libraries: sys/statvfs.h

260. Container-lite (namespaces + cgroups) Description: Isolate a process with namespaces and resource limits. Difficulty: Advanced Topics: namespaces, cgroups, clone Estimated LOC: 700 Libraries: sched.h

261. chroot Jail Runner Description: Run a command inside a chroot with a minimal filesystem. Difficulty: Advanced Topics: chroot, capabilities Estimated LOC: 400 Libraries: unistd.h

262. File Locking Demo (flock/fcntl) Description: Coordinate file access across processes with locks. Difficulty: Intermediate Topics: file locking, concurrency Estimated LOC: 300 Libraries: fcntl.h

263. Terminal Multiplexer (mini-tmux) Description: Run multiple shells via ptys with split panes. Difficulty: Advanced Topics: pty, terminal, multiplexing Estimated LOC: 900 Libraries: pty.h, ncurses

264. uptime/Load Average Reader Description: Report uptime, load averages, and logged-in users. Difficulty: Beginner Topics: /proc, sysinfo Estimated LOC: 200 Libraries: sys/sysinfo.h

265. Signal-Safe Logging Library Description: Async-signal-safe logger usable inside signal handlers. Difficulty: Advanced Topics: signals, reentrancy Estimated LOC: 350 Libraries: unistd.h

266. lsof-lite (open files by process) Description: List open file descriptors per process from /proc/*/fd. Difficulty: Intermediate Topics: /proc, symlinks Estimated LOC: 350 Libraries: dirent.h

267. Battery / Sensor Monitor Description: Read battery, temperature, and fan data from sysfs. Difficulty: Beginner Topics: sysfs, parsing Estimated LOC: 250 Libraries: stdio.h

268. seccomp Syscall Sandbox Description: Restrict a program to an allowlist of syscalls. Difficulty: Advanced Topics: seccomp-bpf, security Estimated LOC: 400 Libraries: seccomp

269. dd-style Block Copier Description: Copy blocks with configurable size, count, and conversions. Difficulty: Intermediate Topics: raw I/O, buffering Estimated LOC: 300 Libraries: unistd.h

270. System Resource Limit (ulimit) Tool Description: Query and set resource limits via getrlimit/setrlimit. Difficulty: Intermediate Topics: rlimits, syscalls Estimated LOC: 250 Libraries: sys/resource.h

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12. Shell Programming (271–283)

271. Minimal Shell (fork/exec) Description: Read, parse, and execute single commands with arguments. Difficulty: Intermediate Topics: fork, exec, wait Estimated LOC: 300 Libraries: unistd.h

272. Shell with Pipes & Redirection Description: Support |, >, <, and >> between commands. Difficulty: Advanced Topics: pipes, dup2, parsing Estimated LOC: 600 Libraries: unistd.h

273. Shell with Built-ins & History Description: Add cd, export, history, and up-arrow recall. Difficulty: Advanced Topics: builtins, line editing Estimated LOC: 700 Libraries: readline

274. Shell Command Autocompletion Description: Tab-complete commands and file paths in your shell. Difficulty: Advanced Topics: readline, completion Estimated LOC: 400 Libraries: readline

275. Shell Scripting Interpreter Description: Interpret a scripting subset with variables, if, and loops. Difficulty: Advanced Topics: parsing, control flow Estimated LOC: 900 Libraries: stdlib.h

276. Alias & Environment Manager Description: Support aliases and per-session environment configuration. Difficulty: Intermediate Topics: hash maps, parsing Estimated LOC: 400 Libraries: stdlib.h

277. Prompt Customization Engine Description: Render a configurable prompt with git status and time. Difficulty: Intermediate Topics: strings, subprocess Estimated LOC: 350 Libraries: unistd.h

278. Command Timing Wrapper (time clone) Description: Measure real/user/sys time for any command. Difficulty: Intermediate Topics: fork, rusage, timing Estimated LOC: 250 Libraries: sys/resource.h

279. Background Job Manager Description: Run commands in the background and manage them with jobs/fg/bg. Difficulty: Advanced Topics: process groups, signals Estimated LOC: 500 Libraries: signal.h

280. Glob Pattern Expander Description: Expand *, ?, and [...] patterns like a shell. Difficulty: Intermediate Topics: pattern matching, dirent Estimated LOC: 350 Libraries: dirent.h

281. Here-Doc & Variable Expansion Engine Description: Implement here-documents and $VAR/${VAR} expansion. Difficulty: Advanced Topics: parsing, substitution Estimated LOC: 400 Libraries: stdlib.h

282. Shell Pipeline Profiler Description: Report per-stage timing and byte throughput in a pipeline. Difficulty: Advanced Topics: pipes, timing, stats Estimated LOC: 450 Libraries: unistd.h

283. Dotfile Manager Description: Symlink and version dotfiles across machines from a config. Difficulty: Intermediate Topics: symlinks, file ops Estimated LOC: 400 Libraries: unistd.h

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13. Networking (TCP/UDP/IP) (284–309)

284. TCP Echo Server & Client Description: A blocking TCP server that echoes back what clients send. Difficulty: Beginner Topics: sockets, TCP Estimated LOC: 250 Libraries: sys/socket.h

285. UDP Echo & Ping Tool Description: Send/receive UDP datagrams and measure round-trip time. Difficulty: Beginner Topics: sockets, UDP Estimated LOC: 250 Libraries: sys/socket.h

286. Concurrent Chat Server (fork/thread) Description: Multi-client chat room broadcasting messages to all peers. Difficulty: Intermediate Topics: sockets, concurrency Estimated LOC: 500 Libraries: pthread

287. Chat Server with select()/poll() Description: Single-threaded multiplexed chat server. Difficulty: Intermediate Topics: I/O multiplexing Estimated LOC: 450 Libraries: sys/select.h

288. High-Concurrency epoll Server Description: Handle thousands of connections with an epoll event loop. Difficulty: Advanced Topics: epoll, non-blocking I/O Estimated LOC: 600 Libraries: sys/epoll.h

289. File Transfer Protocol (custom) Description: Reliable file transfer with chunking and checksums over TCP. Difficulty: Intermediate Topics: sockets, framing Estimated LOC: 500 Libraries: sys/socket.h

290. Port Scanner Description: Scan a host for open TCP ports with connect/SYN modes. Difficulty: Intermediate Topics: sockets, timeouts Estimated LOC: 350 Libraries: sys/socket.h

291. ping (ICMP) Description: Send ICMP echo requests and report latency and loss. Difficulty: Advanced Topics: raw sockets, ICMP, checksums Estimated LOC: 400 Libraries: netinet/ip_icmp.h

292. traceroute Description: Map the route to a host using TTL-limited probes. Difficulty: Advanced Topics: raw sockets, TTL, ICMP Estimated LOC: 450 Libraries: netinet/ip.h

293. DNS Resolver (from scratch) Description: Build and parse DNS queries over UDP without libc resolver. Difficulty: Advanced Topics: DNS wire format, UDP Estimated LOC: 500 Libraries: sys/socket.h

294. DHCP Client (basic) Description: Perform DISCOVER/OFFER/REQUEST/ACK to obtain a lease. Difficulty: Advanced Topics: DHCP, raw sockets Estimated LOC: 600 Libraries: sys/socket.h

295. ARP Scanner Description: Discover hosts on a LAN via ARP requests. Difficulty: Advanced Topics: raw sockets, layer 2 Estimated LOC: 450 Libraries: linux/if_packet.h

296. Packet Sniffer Description: Capture and decode Ethernet/IP/TCP headers off the wire. Difficulty: Advanced Topics: raw sockets, packet parsing Estimated LOC: 600 Libraries: libpcap

297. Bandwidth Meter (iperf-lite) Description: Measure throughput between two hosts over TCP/UDP. Difficulty: Intermediate Topics: sockets, timing Estimated LOC: 450 Libraries: sys/socket.h

298. NTP Time Client Description: Query an NTP server and compute clock offset. Difficulty: Intermediate Topics: NTP protocol, UDP Estimated LOC: 350 Libraries: sys/socket.h

299. Simple VPN Tunnel (TUN device) Description: Tunnel IP packets between hosts through a userspace TUN device. Difficulty: Advanced Topics: TUN/TAP, encryption Estimated LOC: 700 Libraries: linux/if_tun.h

300. TCP Proxy / Port Forwarder Description: Forward connections between a local and remote endpoint. Difficulty: Intermediate Topics: sockets, relaying Estimated LOC: 400 Libraries: sys/socket.h

301. SOCKS5 Proxy Server Description: Implement the SOCKS5 handshake and relay traffic. Difficulty: Advanced Topics: proxy protocols, sockets Estimated LOC: 600 Libraries: sys/socket.h

302. Reliable UDP Protocol Description: Add ACKs, retransmission, and ordering on top of UDP. Difficulty: Advanced Topics: protocol design, reliability Estimated LOC: 700 Libraries: sys/socket.h

303. Network Chat with Encryption Description: End-to-end encrypted chat over TCP with key exchange. Difficulty: Advanced Topics: crypto, sockets Estimated LOC: 700 Libraries: OpenSSL

304. Multicast Group Messenger Description: Send and receive on IP multicast groups. Difficulty: Intermediate Topics: multicast, UDP Estimated LOC: 350 Libraries: sys/socket.h

305. WHOIS Client Description: Query WHOIS servers and display registration data. Difficulty: Beginner Topics: sockets, protocols Estimated LOC: 250 Libraries: sys/socket.h

306. mDNS / Service Discovery Description: Advertise and discover services on the local network. Difficulty: Advanced Topics: mDNS, multicast Estimated LOC: 600 Libraries: sys/socket.h

307. Simple BitTorrent Peer (leech) Description: Parse a .torrent, contact peers, and download pieces. Difficulty: Advanced Topics: bencode, peer protocol Estimated LOC: 1200 Libraries: OpenSSL

308. Syslog Server Description: Receive and store RFC-5424 syslog messages over UDP. Difficulty: Intermediate Topics: parsing, UDP Estimated LOC: 400 Libraries: sys/socket.h

309. Load Balancer (round-robin/least-conn) Description: Distribute TCP connections across backend servers. Difficulty: Advanced Topics: proxying, health checks Estimated LOC: 700 Libraries: sys/epoll.h

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14. Web Servers, HTTP & REST (310–329)

310. HTTP/1.0 Static File Server Description: Serve files from a directory with correct MIME types. Difficulty: Intermediate Topics: HTTP, sockets, file I/O Estimated LOC: 500 Libraries: sys/socket.h

311. HTTP Request Parser Description: Parse request line, headers, and body robustly. Difficulty: Intermediate Topics: parsing, HTTP Estimated LOC: 400 Libraries: stdlib.h

312. HTTP Client (curl-lite) Description: Perform GET/POST requests and print responses. Difficulty: Intermediate Topics: HTTP, sockets Estimated LOC: 450 Libraries: sys/socket.h

313. HTTP/1.1 Server with Keep-Alive Description: Persistent connections, chunked encoding, and pipelining. Difficulty: Advanced Topics: HTTP/1.1, streaming Estimated LOC: 800 Libraries: sys/socket.h

314. REST API Server (in-memory) Description: CRUD JSON REST endpoints backed by an in-memory store. Difficulty: Advanced Topics: HTTP, JSON, routing Estimated LOC: 900 Libraries: sys/socket.h

315. URL Router & Middleware Framework Description: Route requests by method/path with composable middleware. Difficulty: Advanced Topics: routing, function pointers Estimated LOC: 600 Libraries: stdlib.h

316. WebSocket Server Description: Perform the WS handshake and exchange framed messages. Difficulty: Advanced Topics: WebSocket, framing, SHA-1 Estimated LOC: 700 Libraries: OpenSSL

317. HTTPS Server with TLS Description: Serve HTTP over TLS using OpenSSL. Difficulty: Advanced Topics: TLS, sockets Estimated LOC: 700 Libraries: OpenSSL

318. CGI Web Server Description: Execute CGI scripts and stream their output to clients. Difficulty: Advanced Topics: fork/exec, environ, HTTP Estimated LOC: 700 Libraries: unistd.h

319. Reverse Proxy Description: Forward HTTP requests to backends and relay responses. Difficulty: Advanced Topics: HTTP, proxying Estimated LOC: 800 Libraries: sys/socket.h

320. HTTP Rate Limiter Description: Throttle requests per client using token buckets. Difficulty: Intermediate Topics: algorithms, HTTP Estimated LOC: 400 Libraries: stdlib.h

321. Static Site Generator Description: Convert Markdown + templates into a static website. Difficulty: Intermediate Topics: parsing, templating, file I/O Estimated LOC: 700 Libraries: stdio.h

322. URL Shortener Service Description: Map short codes to URLs with a REST API and persistence. Difficulty: Intermediate Topics: HTTP, hashing, storage Estimated LOC: 600 Libraries: sys/socket.h

323. HTTP Cache / CDN-lite Description: Cache upstream responses with TTL and revalidation. Difficulty: Advanced Topics: caching, HTTP semantics Estimated LOC: 700 Libraries: sys/socket.h

324. Cookie & Session Manager Description: Issue and validate session cookies with signing. Difficulty: Intermediate Topics: HTTP, HMAC Estimated LOC: 400 Libraries: OpenSSL

325. JSON REST Client SDK Generator Description: Generate typed C client stubs from an API description. Difficulty: Advanced Topics: code generation, parsing Estimated LOC: 700 Libraries: stdlib.h

326. Server-Sent Events (SSE) Server Description: Stream real-time events to browsers over HTTP. Difficulty: Intermediate Topics: HTTP streaming Estimated LOC: 400 Libraries: sys/socket.h

327. Multipart Form Upload Handler Description: Parse multipart/form-data and save uploaded files. Difficulty: Advanced Topics: parsing, HTTP Estimated LOC: 500 Libraries: stdlib.h

328. Basic + Bearer Auth Middleware Description: Protect routes with HTTP Basic and token auth. Difficulty: Intermediate Topics: HTTP auth, base64 Estimated LOC: 350 Libraries: OpenSSL

329. Webhook Dispatcher Description: Queue and deliver HTTP webhooks with retries and backoff. Difficulty: Advanced Topics: HTTP client, queues, retries Estimated LOC: 600 Libraries: sys/socket.h

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15. Multithreading & Concurrency (330–349)

330. Thread Pool Description: A fixed pool of worker threads consuming a task queue. Difficulty: Intermediate Topics: pthreads, queues, condvars Estimated LOC: 400 Libraries: pthread

331. Parallel Merge Sort Description: Sort large arrays using worker threads. Difficulty: Intermediate Topics: parallelism, divide and conquer Estimated LOC: 350 Libraries: pthread

332. Producer-Consumer Queue (bounded) Description: Thread-safe bounded buffer with condition variables. Difficulty: Intermediate Topics: synchronization Estimated LOC: 300 Libraries: pthread

333. Read-Write Lock Library Description: Implement fair reader-writer locks from primitives. Difficulty: Advanced Topics: synchronization, fairness Estimated LOC: 350 Libraries: pthread

334. Lock-Free Queue (CAS) Description: Michael-Scott lock-free MPSC/MPMC queue with atomics. Difficulty: Advanced Topics: atomics, memory ordering Estimated LOC: 450 Libraries: stdatomic.h

335. Parallel Web Crawler Description: Crawl links concurrently with a shared frontier. Difficulty: Advanced Topics: threads, HTTP, dedup Estimated LOC: 800 Libraries: pthread

336. Map-Reduce Framework (single node) Description: Run map/reduce jobs across worker threads. Difficulty: Advanced Topics: parallelism, aggregation Estimated LOC: 600 Libraries: pthread

337. Actor Model Runtime Description: Message-passing actors with mailboxes and a scheduler. Difficulty: Advanced Topics: concurrency models Estimated LOC: 700 Libraries: pthread

338. Parallel Matrix Multiply Description: Multiply large matrices with tiling and threads. Difficulty: Intermediate Topics: parallelism, cache blocking Estimated LOC: 400 Libraries: pthread

339. Barrier & Latch Primitives Description: Implement reusable barriers and countdown latches. Difficulty: Intermediate Topics: synchronization Estimated LOC: 300 Libraries: pthread

340. Coroutine Library (setjmp/ucontext) Description: Cooperative coroutines with yield and resume. Difficulty: Advanced Topics: context switching Estimated LOC: 400 Libraries: ucontext.h

341. Parallel Prime Sieve Description: Segment the sieve across threads for speed. Difficulty: Intermediate Topics: parallelism, number theory Estimated LOC: 350 Libraries: pthread

342. Concurrent Hash Map Description: Thread-safe hash map with fine-grained locking. Difficulty: Advanced Topics: concurrency, hashing Estimated LOC: 500 Libraries: pthread

343. Work-Stealing Scheduler Description: Balance tasks across threads with per-thread deques. Difficulty: Advanced Topics: scheduling, deques Estimated LOC: 600 Libraries: pthread

344. Deadlock Detector (runtime) Description: Instrument locks to detect lock-order cycles at runtime. Difficulty: Advanced Topics: graphs, synchronization Estimated LOC: 500 Libraries: pthread

345. Parallel Image Filter Description: Apply convolution filters to images across threads. Difficulty: Intermediate Topics: parallelism, image processing Estimated LOC: 400 Libraries: pthread

346. Thread-Safe Logger Description: Non-blocking logging with a background flush thread. Difficulty: Intermediate Topics: queues, threads Estimated LOC: 400 Libraries: pthread

347. Futures / Promises Library Description: Async result handles resolved by worker threads. Difficulty: Advanced Topics: concurrency abstractions Estimated LOC: 450 Libraries: pthread

348. Parallel Monte Carlo Simulator Description: Run independent simulations across cores and merge results. Difficulty: Intermediate Topics: parallelism, RNG per-thread Estimated LOC: 350 Libraries: pthread

349. SIMD-Accelerated Vector Ops Description: Speed up array math with SSE/AVX intrinsics. Difficulty: Advanced Topics: SIMD, intrinsics Estimated LOC: 400 Libraries: immintrin.h

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16. Memory Management (350–366)

350. Custom malloc/free (free list) Description: A heap allocator using a free list and sbrk/mmap. Difficulty: Advanced Topics: allocators, memory Estimated LOC: 600 Libraries: unistd.h

351. Arena / Bump Allocator Description: Fast region allocator with bulk free. Difficulty: Intermediate Topics: allocators, lifetimes Estimated LOC: 250 Libraries: stdlib.h

352. Pool / Slab Allocator Description: Fixed-size object pool to avoid fragmentation. Difficulty: Intermediate Topics: allocators, free lists Estimated LOC: 300 Libraries: stdlib.h

353. Stack Allocator Description: LIFO allocator with save/restore markers. Difficulty: Intermediate Topics: allocators Estimated LOC: 250 Libraries: stdlib.h

354. Reference-Counting Smart Pointers Description: Retain/release semantics with automatic free. Difficulty: Advanced Topics: reference counting Estimated LOC: 350 Libraries: stdlib.h

355. Mark-and-Sweep Garbage Collector Description: A tracing GC for a managed object graph. Difficulty: Advanced Topics: garbage collection Estimated LOC: 600 Libraries: stdlib.h

356. Generational / Copying GC Description: Copying collector with young/old generations. Difficulty: Advanced Topics: garbage collection Estimated LOC: 800 Libraries: stdlib.h

357. Memory Leak Detector Description: Wrap malloc/free to report leaks and double-frees. Difficulty: Advanced Topics: instrumentation, hooks Estimated LOC: 450 Libraries: dlfcn.h

358. Buffer Overflow Guard Allocator Description: Add guard pages/canaries around allocations. Difficulty: Advanced Topics: mprotect, security Estimated LOC: 400 Libraries: sys/mman.h

359. Memory Debugger (Valgrind-lite) Description: Track allocations and detect invalid accesses via interposition. Difficulty: Advanced Topics: instrumentation, shadow memory Estimated LOC: 700 Libraries: dlfcn.h

360. Object Pool with Recycling Description: Reuse expensive objects with acquire/release. Difficulty: Intermediate Topics: pooling, lifetimes Estimated LOC: 300 Libraries: stdlib.h

361. Copy-on-Write Buffer Description: Share buffers cheaply and copy only on mutation. Difficulty: Advanced Topics: COW, reference counting Estimated LOC: 400 Libraries: stdlib.h

362. Compacting Allocator Description: Reduce fragmentation by relocating live objects. Difficulty: Advanced Topics: memory compaction Estimated LOC: 600 Libraries: stdlib.h

363. Custom realloc Growth Strategy Benchmark Description: Compare growth factors and their fragmentation impact. Difficulty: Intermediate Topics: allocators, benchmarking Estimated LOC: 350 Libraries: time.h

364. Aligned Allocation Library Description: Provide cache-line and page-aligned allocations. Difficulty: Intermediate Topics: alignment, memory Estimated LOC: 250 Libraries: stdlib.h

365. Memory Fragmentation Visualizer Description: Visualize heap layout and fragmentation over time. Difficulty: Advanced Topics: allocators, visualization Estimated LOC: 500 Libraries: ncurses

366. Stack Depth & Overflow Detector Description: Detect deep recursion and near-stack-overflow conditions. Difficulty: Advanced Topics: stack, signals, guard pages Estimated LOC: 350 Libraries: signal.h

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17. Graphics (SDL2 / Raylib / OpenGL) (367–392)

367. Software Framebuffer Renderer Description: Plot pixels, lines, and shapes into a raw framebuffer. Difficulty: Intermediate Topics: rasterization, Bresenham Estimated LOC: 500 Libraries: SDL2

368. Line & Circle Rasterizer Description: Draw primitives using Bresenham and midpoint algorithms. Difficulty: Intermediate Topics: rasterization Estimated LOC: 350 Libraries: SDL2

369. Triangle Rasterizer with Z-Buffer Description: Fill triangles with depth testing and interpolation. Difficulty: Advanced Topics: rasterization, 3D Estimated LOC: 600 Libraries: SDL2

370. Software 3D Wireframe Renderer Description: Project and draw 3D models as rotating wireframes. Difficulty: Advanced Topics: 3D math, projection Estimated LOC: 600 Libraries: SDL2

371. Software 3D Renderer with Shading Description: Flat/Gouraud shading of OBJ models in software. Difficulty: Advanced Topics: 3D graphics, lighting Estimated LOC: 900 Libraries: SDL2

372. Ray Tracer (spheres & planes) Description: Render scenes with reflections, shadows, and lighting. Difficulty: Advanced Topics: ray tracing, vectors Estimated LOC: 900 Libraries: none (PPM output)

373. Path Tracer Description: Physically based rendering with Monte Carlo sampling. Difficulty: Advanced Topics: global illumination, sampling Estimated LOC: 1200 Libraries: none (PPM output)

374. OBJ Model Loader & Viewer Description: Parse Wavefront OBJ and view it with OpenGL. Difficulty: Advanced Topics: parsing, OpenGL Estimated LOC: 700 Libraries: OpenGL, GLFW

375. 2D Particle System Description: Simulate fire/smoke/sparks with thousands of particles. Difficulty: Intermediate Topics: simulation, rendering Estimated LOC: 500 Libraries: Raylib

376. Fractal Explorer (Mandelbrot/Julia) Description: Interactive zoomable fractal viewer with color maps. Difficulty: Intermediate Topics: complex math, rendering Estimated LOC: 500 Libraries: SDL2

377. Fluid Simulation (Stam's stable fluids) Description: Real-time 2D fluid with advection and diffusion. Difficulty: Advanced Topics: numerical simulation Estimated LOC: 800 Libraries: SDL2

378. Cloth / Spring-Mass Simulation Description: Simulate cloth with constraints and gravity. Difficulty: Advanced Topics: physics, integration Estimated LOC: 600 Libraries: Raylib

379. Boids Flocking Simulation Description: Emergent flocking from separation/alignment/cohesion. Difficulty: Intermediate Topics: simulation, vectors Estimated LOC: 400 Libraries: Raylib

380. Procedural Terrain Generator Description: Generate and render terrain from Perlin/Simplex noise. Difficulty: Advanced Topics: noise, meshes Estimated LOC: 700 Libraries: Raylib

381. Voxel Engine (mini-Minecraft) Description: Render and edit a chunked voxel world. Difficulty: Advanced Topics: meshing, chunks, OpenGL Estimated LOC: 1500 Libraries: OpenGL, GLFW

382. 2D Physics Engine Description: Rigid-body collisions, impulses, and constraints. Difficulty: Advanced Topics: physics, collision detection Estimated LOC: 1000 Libraries: SDL2

383. Bezier & Spline Editor Description: Interactively edit and render Bezier/Catmull-Rom curves. Difficulty: Intermediate Topics: curves, interpolation Estimated LOC: 450 Libraries: Raylib

384. Image Viewer with Zoom/Pan Description: Load and navigate images with smooth zoom. Difficulty: Intermediate Topics: textures, input Estimated LOC: 400 Libraries: SDL2, stb_image

385. Font Renderer (bitmap/TTF) Description: Rasterize text from bitmap or TrueType fonts. Difficulty: Advanced Topics: glyphs, rasterization Estimated LOC: 700 Libraries: stb_truetype

386. Simple Paint Program Description: Draw with brushes, colors, layers, and export to PNG. Difficulty: Intermediate Topics: input, rendering, files Estimated LOC: 700 Libraries: SDL2

387. Charting / Plotting Library Description: Render line, bar, and scatter charts to an image. Difficulty: Intermediate Topics: rendering, scaling Estimated LOC: 600 Libraries: Raylib

388. Marching Squares / Contour Renderer Description: Extract and draw contour lines from a scalar field. Difficulty: Advanced Topics: computational geometry Estimated LOC: 450 Libraries: SDL2

389. Software Shader Playground Description: Run per-pixel "shaders" (C callbacks) over a framebuffer. Difficulty: Advanced Topics: rendering, function pointers Estimated LOC: 500 Libraries: SDL2

390. Sprite Animation System Description: Load sprite sheets and play frame-based animations. Difficulty: Intermediate Topics: textures, timing Estimated LOC: 400 Libraries: Raylib

391. Isometric Tile Renderer Description: Render and pick tiles in an isometric grid world. Difficulty: Advanced Topics: coordinate transforms Estimated LOC: 600 Libraries: SDL2

392. GPU Compute with OpenGL Compute Shaders Description: Offload a parallel computation (N-body) to the GPU. Difficulty: Advanced Topics: GPGPU, OpenGL Estimated LOC: 700 Libraries: OpenGL, GLFW

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18. ncurses & Terminal UIs (393–408)

393. Terminal Text Editor (nano-lite) Description: Modal-free editor with cursor movement, edit, and save. Difficulty: Advanced Topics: ncurses, buffers, input Estimated LOC: 800 Libraries: ncurses

394. Vim-like Modal Editor Description: Editor with normal/insert modes and basic motions. Difficulty: Advanced Topics: modal input, buffers Estimated LOC: 1200 Libraries: ncurses

395. Terminal File Manager (ranger-lite) Description: Navigate directories with a two-pane preview UI. Difficulty: Advanced Topics: ncurses, filesystem Estimated LOC: 900 Libraries: ncurses

396. TUI Dashboard Framework Description: Composable widgets (boxes, gauges, tables) for TUIs. Difficulty: Advanced Topics: layout, widgets Estimated LOC: 900 Libraries: ncurses

397. Terminal Task Board (Kanban) Description: Drag tasks across columns with keyboard controls. Difficulty: Intermediate Topics: ncurses, state, persistence Estimated LOC: 600 Libraries: ncurses

398. Terminal Music Player UI Description: Browse and control playback with a progress bar. Difficulty: Advanced Topics: ncurses, audio integration Estimated LOC: 700 Libraries: ncurses, libao

399. Terminal Spreadsheet Description: Grid of cells with formulas and dependency recalculation. Difficulty: Advanced Topics: parsing, dependency graphs Estimated LOC: 900 Libraries: ncurses

400. Terminal Hex Editor Description: View and edit binary files in a hex/ASCII pane. Difficulty: Advanced Topics: ncurses, binary I/O Estimated LOC: 700 Libraries: ncurses

401. Terminal Git Log Browser Description: Interactively browse commits and diffs. Difficulty: Advanced Topics: ncurses, subprocess parsing Estimated LOC: 700 Libraries: ncurses

402. Terminal Process Manager Description: Interactive process list with kill/renice actions. Difficulty: Advanced Topics: ncurses, /proc Estimated LOC: 700 Libraries: ncurses

403. Terminal Chart Viewer Description: Render live line/bar charts from piped data. Difficulty: Intermediate Topics: ncurses, plotting Estimated LOC: 500 Libraries: ncurses

404. TUI Form & Menu Library Description: Build forms with fields, validation, and menus. Difficulty: Intermediate Topics: ncurses forms Estimated LOC: 500 Libraries: ncurses (form/menu)

405. Terminal Calendar & Agenda Description: Month view with events and day agenda pane. Difficulty: Intermediate Topics: ncurses, date math Estimated LOC: 500 Libraries: ncurses

406. Terminal Presentation Tool Description: Show Markdown slides in the terminal with transitions. Difficulty: Intermediate Topics: parsing, ncurses Estimated LOC: 500 Libraries: ncurses

407. Terminal Typing Speed Test Description: Measure WPM/accuracy with live highlighting. Difficulty: Beginner Topics: ncurses, timing Estimated LOC: 350 Libraries: ncurses

408. TUI Log Tailer with Filters Description: Follow logs with search, highlight, and level filters. Difficulty: Intermediate Topics: ncurses, streaming Estimated LOC: 500 Libraries: ncurses

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19. Cryptography (409–431)

409. Classical Cipher Suite Description: Caesar, Vigenère, Playfair, and rail-fence with cryptanalysis. Difficulty: Intermediate Topics: substitution ciphers, frequency analysis Estimated LOC: 500 Libraries: ctype.h

410. XOR Cipher & Key Recovery Description: Encrypt with repeating-key XOR and break it statistically. Difficulty: Intermediate Topics: XOR, frequency analysis Estimated LOC: 350 Libraries: stdlib.h

411. MD5 Implementation Description: Implement the MD5 hash from the spec. Difficulty: Advanced Topics: hashing, bit operations Estimated LOC: 400 Libraries: stdint.h

412. SHA-256 Implementation Description: Implement SHA-256 and verify against test vectors. Difficulty: Advanced Topics: hashing, bit operations Estimated LOC: 400 Libraries: stdint.h

413. SHA-3 / Keccak Implementation Description: Implement the Keccak sponge and SHA-3 variants. Difficulty: Advanced Topics: hashing, permutations Estimated LOC: 600 Libraries: stdint.h

414. HMAC Library Description: Compute HMAC over any hash and verify messages. Difficulty: Intermediate Topics: MACs, hashing Estimated LOC: 250 Libraries: stdint.h

415. AES (128/256) Implementation Description: Implement AES block cipher with ECB/CBC/CTR modes. Difficulty: Advanced Topics: block ciphers, GF(2^8) Estimated LOC: 800 Libraries: stdint.h

416. ChaCha20 + Poly1305 AEAD Description: Implement authenticated stream encryption. Difficulty: Advanced Topics: stream ciphers, AEAD Estimated LOC: 600 Libraries: stdint.h

417. RSA Key Generation & Encryption Description: Generate keys and encrypt/sign with big-integer RSA. Difficulty: Advanced Topics: number theory, bignum Estimated LOC: 900 Libraries: GMP (or custom bignum)

418. Diffie-Hellman Key Exchange Description: Establish a shared secret over an insecure channel. Difficulty: Advanced Topics: modular exponentiation Estimated LOC: 400 Libraries: GMP

419. Elliptic Curve Point Arithmetic Description: Implement point addition/doubling on curve25519. Difficulty: Advanced Topics: ECC, modular math Estimated LOC: 700 Libraries: stdint.h

420. Base64 / Base32 / Base58 Codec Description: Encode and decode common binary-to-text encodings. Difficulty: Beginner Topics: bit manipulation, encoding Estimated LOC: 350 Libraries: stdint.h

421. Password Hashing (PBKDF2/bcrypt-style) Description: Derive keys with salt and configurable iterations. Difficulty: Advanced Topics: KDFs, hashing Estimated LOC: 500 Libraries: stdint.h

422. Shamir's Secret Sharing Description: Split a secret into shares requiring k-of-n to recover. Difficulty: Advanced Topics: polynomials, finite fields Estimated LOC: 500 Libraries: stdlib.h

423. Digital Signature Tool (sign/verify) Description: Sign files with a private key and verify signatures. Difficulty: Advanced Topics: signatures, hashing Estimated LOC: 500 Libraries: OpenSSL

424. TOTP / HOTP Authenticator Description: Generate one-time passwords compatible with 2FA apps. Difficulty: Intermediate Topics: HMAC, time-based codes Estimated LOC: 300 Libraries: stdint.h

425. Cryptographic RNG (CSPRNG) Description: Gather entropy and produce secure random bytes. Difficulty: Advanced Topics: entropy, hashing Estimated LOC: 350 Libraries: unistd.h

426. Encrypted File Vault Description: Password-protected vault with authenticated encryption. Difficulty: Advanced Topics: AEAD, KDF, file I/O Estimated LOC: 600 Libraries: libsodium

427. Merkle Tree Builder & Proofs Description: Build Merkle trees and generate inclusion proofs. Difficulty: Advanced Topics: hashing, trees Estimated LOC: 450 Libraries: stdint.h

428. Steganography Tool (LSB) Description: Hide and extract messages in image pixels. Difficulty: Intermediate Topics: image bytes, bit manipulation Estimated LOC: 400 Libraries: stb_image

429. One-Time Pad with Key Management Description: Perfectly-secret encryption with key generation and tracking. Difficulty: Intermediate Topics: XOR, key handling Estimated LOC: 300 Libraries: unistd.h

430. CRC32 / Checksum Library Description: Implement CRC and Adler checksums with tables. Difficulty: Intermediate Topics: polynomial arithmetic Estimated LOC: 300 Libraries: stdint.h

431. Simple TLS 1.2 Handshake (educational) Description: Perform a minimal TLS handshake using primitives you built. Difficulty: Advanced Topics: TLS, crypto composition Estimated LOC: 1500 Libraries: (self-built primitives)

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20. Security, Reverse Engineering & Binary Analysis (432–457)

432. Buffer Overflow Demo & Mitigation Lab Description: Demonstrate and then defend against a stack overflow. Difficulty: Advanced Topics: memory safety, canaries Estimated LOC: 400 Libraries: none

433. Format String Vulnerability Lab Description: Exploit and fix a printf format-string bug. Difficulty: Advanced Topics: vulnerabilities, mitigation Estimated LOC: 300 Libraries: none

434. Shellcode Loader & Runner Description: Load and execute position-independent shellcode (for research). Difficulty: Advanced Topics: mmap, exec permissions Estimated LOC: 300 Libraries: sys/mman.h

435. ELF Symbol & Section Dumper (readelf-lite) Description: Parse and display ELF sections, symbols, and relocations. Difficulty: Advanced Topics: ELF, binary layout Estimated LOC: 600 Libraries: elf.h

436. x86 Disassembler (subset) Description: Decode a subset of x86-64 instructions to assembly. Difficulty: Advanced Topics: instruction encoding Estimated LOC: 900 Libraries: none

437. Simple Debugger (ptrace) Description: Set breakpoints, single-step, and inspect registers. Difficulty: Advanced Topics: ptrace, breakpoints Estimated LOC: 700 Libraries: sys/ptrace.h

438. Function Hooking / Detour Library Description: Redirect function calls at runtime by patching prologues. Difficulty: Advanced Topics: code patching, mprotect Estimated LOC: 500 Libraries: sys/mman.h

439. LD_PRELOAD Interposition Toolkit Description: Intercept libc calls to log or modify behavior. Difficulty: Advanced Topics: dynamic linking, hooks Estimated LOC: 350 Libraries: dlfcn.h

440. PE (Windows Executable) Parser Description: Parse PE headers, sections, and imports. Difficulty: Advanced Topics: PE format, binary layout Estimated LOC: 600 Libraries: stdint.h

441. Control Flow Graph Extractor Description: Build a CFG from a disassembled function. Difficulty: Advanced Topics: static analysis, graphs Estimated LOC: 600 Libraries: none

442. Fuzzer (coverage-guided lite) Description: Mutate inputs and detect crashes in a target program. Difficulty: Advanced Topics: fuzzing, instrumentation Estimated LOC: 600 Libraries: none

443. String & Entropy Scanner (strings clone) Description: Extract printable strings and flag high-entropy regions. Difficulty: Intermediate Topics: binary scanning, entropy Estimated LOC: 350 Libraries: math.h

444. Yara-style Signature Scanner Description: Match byte/string patterns against files with rules. Difficulty: Advanced Topics: pattern matching, rules Estimated LOC: 600 Libraries: stdlib.h

445. Packer / Unpacker (educational) Description: Compress+encrypt a binary and unpack it at runtime. Difficulty: Advanced Topics: loaders, compression Estimated LOC: 700 Libraries: zlib

446. ROP Gadget Finder Description: Scan a binary for useful return-oriented gadgets. Difficulty: Advanced Topics: disassembly, exploitation research Estimated LOC: 500 Libraries: none

447. Anti-Debugging Detection Demo Description: Detect ptrace/debugger presence and time-based checks. Difficulty: Advanced Topics: ptrace, timing Estimated LOC: 300 Libraries: sys/ptrace.h

448. Simple Antivirus (signature-based) Description: Scan files against a hash/signature database. Difficulty: Intermediate Topics: hashing, scanning Estimated LOC: 500 Libraries: OpenSSL

449. Network Intrusion Detector (rules) Description: Match packet patterns and alert on suspicious traffic. Difficulty: Advanced Topics: packet parsing, rules Estimated LOC: 700 Libraries: libpcap

450. Password Strength Auditor Description: Score passwords and check against common wordlists. Difficulty: Intermediate Topics: entropy, dictionaries Estimated LOC: 350 Libraries: stdlib.h

451. Dictionary/Brute-Force Cracker (own hashes) Description: Crack self-generated hashed passwords for education. Difficulty: Intermediate Topics: hashing, search Estimated LOC: 400 Libraries: OpenSSL

452. Syscall Auditing Sandbox Description: Log and restrict syscalls of an untrusted child (ptrace/seccomp). Difficulty: Advanced Topics: ptrace, seccomp, security Estimated LOC: 600 Libraries: seccomp

453. Binary Diffing Tool Description: Compare two binaries at the function/byte level. Difficulty: Advanced Topics: diffing, disassembly Estimated LOC: 600 Libraries: none

454. Import/Dependency Analyzer (ldd-lite) Description: List shared library dependencies of an executable. Difficulty: Intermediate Topics: ELF, dynamic section Estimated LOC: 400 Libraries: elf.h

455. Heap Exploitation Sandbox Description: Visualize allocator internals to study heap bugs safely. Difficulty: Advanced Topics: allocators, memory safety Estimated LOC: 600 Libraries: none

456. Capability & Privilege Dropper Description: Safely drop privileges and Linux capabilities after setup. Difficulty: Advanced Topics: capabilities, security Estimated LOC: 300 Libraries: sys/capability.h

457. Rootkit Detection Scanner (userspace) Description: Detect hidden processes/files by cross-checking sources. Difficulty: Advanced Topics: /proc, anomaly detection Estimated LOC: 500 Libraries: dirent.h

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21. Image Processing (458–476)

458. PPM/PGM Image Library Description: Read, write, and manipulate Netpbm images. Difficulty: Beginner Topics: image formats, I/O Estimated LOC: 300 Libraries: stdio.h

459. Image Filter Toolkit Description: Apply blur, sharpen, edge, and emboss convolutions. Difficulty: Intermediate Topics: convolution, kernels Estimated LOC: 500 Libraries: stb_image

460. Grayscale, Threshold & Histogram Description: Convert to grayscale and compute/equalize histograms. Difficulty: Beginner Topics: pixel math, statistics Estimated LOC: 350 Libraries: stb_image

461. Image Resizer (bilinear/bicubic) Description: Scale images with quality interpolation. Difficulty: Intermediate Topics: interpolation, sampling Estimated LOC: 400 Libraries: stb_image

462. Canny Edge Detector Description: Full Canny pipeline with NMS and hysteresis. Difficulty: Advanced Topics: gradients, edge detection Estimated LOC: 600 Libraries: stb_image

463. Image Rotation & Affine Transform Description: Rotate/skew images with inverse mapping. Difficulty: Intermediate Topics: transforms, sampling Estimated LOC: 400 Libraries: stb_image

464. Seam Carving (content-aware resize) Description: Remove low-energy seams to resize without distortion. Difficulty: Advanced Topics: dynamic programming, energy maps Estimated LOC: 600 Libraries: stb_image

465. Median / Bilateral Denoise Description: Reduce noise while preserving edges. Difficulty: Intermediate Topics: filtering, windows Estimated LOC: 400 Libraries: stb_image

466. Chroma Key (green screen) Description: Composite a subject onto a new background. Difficulty: Intermediate Topics: color spaces, masking Estimated LOC: 350 Libraries: stb_image

467. Image to ASCII Art Description: Convert images into shaded ASCII/ANSI art. Difficulty: Beginner Topics: sampling, mapping Estimated LOC: 300 Libraries: stb_image

468. Dithering (Floyd-Steinberg) Description: Reduce color depth with error-diffusion dithering. Difficulty: Intermediate Topics: quantization, dithering Estimated LOC: 350 Libraries: stb_image

469. Connected Component Labeling Description: Segment and label distinct regions in a binary image. Difficulty: Intermediate Topics: union-find, flood fill Estimated LOC: 400 Libraries: stb_image

470. Hough Transform (lines/circles) Description: Detect lines and circles via the Hough transform. Difficulty: Advanced Topics: accumulators, geometry Estimated LOC: 500 Libraries: stb_image

471. Image Morphing / Blending Description: Cross-dissolve and warp between two images. Difficulty: Advanced Topics: interpolation, warping Estimated LOC: 500 Libraries: stb_image

472. Barcode / QR Decoder Description: Detect and decode 1D/2D codes from an image. Difficulty: Advanced Topics: image processing, decoding Estimated LOC: 900 Libraries: stb_image

473. Panorama Stitcher (basic) Description: Align and blend overlapping photos into a panorama. Difficulty: Advanced Topics: feature matching, homography Estimated LOC: 900 Libraries: stb_image

474. Color Palette Extractor (k-means) Description: Extract dominant colors via k-means clustering. Difficulty: Intermediate Topics: clustering Estimated LOC: 400 Libraries: stb_image

475. Image Format Converter Description: Convert between PNG/JPG/BMP/PPM. Difficulty: Intermediate Topics: codecs, I/O Estimated LOC: 350 Libraries: stb_image, stb_image_write

476. Real-Time Webcam Filter (V4L2) Description: Capture webcam frames and apply live filters. Difficulty: Advanced Topics: V4L2, image processing Estimated LOC: 700 Libraries: linux/videodev2.h, SDL2

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22. Audio & Signal Processing (477–492)

477. WAV Tone Generator Description: Synthesize sine/square/saw tones to a WAV file. Difficulty: Beginner Topics: audio, sampling Estimated LOC: 300 Libraries: stdint.h

478. Audio Playback Engine Description: Stream PCM audio to speakers with a callback API. Difficulty: Intermediate Topics: audio output, buffering Estimated LOC: 400 Libraries: PortAudio (or SDL2)

479. Real-Time Spectrum Analyzer Description: Show a live FFT spectrum of microphone input. Difficulty: Advanced Topics: FFT, audio input Estimated LOC: 600 Libraries: PortAudio, ncurses

480. Digital Audio Filters (EQ) Description: Implement low/high/band-pass biquad filters. Difficulty: Advanced Topics: DSP, filter design Estimated LOC: 500 Libraries: math.h

481. Audio Effects Rack Description: Add reverb, delay, distortion, and chorus effects. Difficulty: Advanced Topics: DSP, buffers Estimated LOC: 700 Libraries: PortAudio

482. Metronome & Beat Generator Description: Precisely timed click track with adjustable BPM. Difficulty: Beginner Topics: timing, audio Estimated LOC: 250 Libraries: SDL2

483. Pitch Detector (autocorrelation) Description: Estimate the fundamental frequency of a note. Difficulty: Advanced Topics: DSP, autocorrelation Estimated LOC: 450 Libraries: math.h

484. Guitar Tuner Description: Detect pitch and show tuning offset in real time. Difficulty: Advanced Topics: DSP, audio input Estimated LOC: 500 Libraries: PortAudio

485. Simple Synthesizer (subtractive) Description: Play notes from the keyboard with oscillators and ADSR. Difficulty: Advanced Topics: synthesis, envelopes Estimated LOC: 700 Libraries: PortAudio, SDL2

486. MIDI File Parser & Player Description: Parse MIDI files and synthesize the notes. Difficulty: Advanced Topics: MIDI format, synthesis Estimated LOC: 700 Libraries: PortAudio

487. DTMF Encoder/Decoder Description: Generate and detect phone touch-tone signals. Difficulty: Intermediate Topics: Goertzel algorithm, DSP Estimated LOC: 400 Libraries: math.h

488. Audio Waveform Visualizer Description: Draw scrolling waveforms of live or file audio. Difficulty: Intermediate Topics: rendering, audio Estimated LOC: 450 Libraries: SDL2

489. Sample Rate Converter (resampler) Description: Resample audio with windowed-sinc interpolation. Difficulty: Advanced Topics: DSP, interpolation Estimated LOC: 500 Libraries: math.h

490. Voice Activity Detector Description: Detect speech vs silence in an audio stream. Difficulty: Intermediate Topics: energy/zero-crossing analysis Estimated LOC: 350 Libraries: math.h

491. Simple Audio Compressor/Limiter Description: Apply dynamic range compression to audio. Difficulty: Advanced Topics: DSP, envelope following Estimated LOC: 450 Libraries: math.h

492. Morse Code Audio Encoder/Decoder Description: Convert text to Morse beeps and decode them back. Difficulty: Intermediate Topics: timing, DSP, encoding Estimated LOC: 400 Libraries: SDL2

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23. Compression (493–505)

493. Run-Length Encoding Description: Compress and decompress data with RLE. Difficulty: Beginner Topics: encoding, streams Estimated LOC: 200 Libraries: stdio.h

494. Huffman File Compressor Description: Full Huffman codec with a serialized code table. Difficulty: Advanced Topics: greedy, trees, bit I/O Estimated LOC: 600 Libraries: stdlib.h

495. LZ77 Compressor Description: Sliding-window dictionary compression. Difficulty: Advanced Topics: LZ77, windows Estimated LOC: 600 Libraries: stdlib.h

496. LZ78 / LZW Compressor Description: Dictionary-building compression like GIF/compress. Difficulty: Advanced Topics: LZW, dictionaries Estimated LOC: 500 Libraries: stdlib.h

497. DEFLATE Implementation Description: Combine LZ77 and Huffman like gzip's DEFLATE. Difficulty: Advanced Topics: LZ77, Huffman, bit streams Estimated LOC: 1000 Libraries: stdlib.h

498. Arithmetic Coder Description: Range/arithmetic coding for near-entropy compression. Difficulty: Advanced Topics: entropy coding, probability Estimated LOC: 600 Libraries: stdlib.h

499. Burrows-Wheeler Transform + MTF Description: Implement BWT, MTF, and RLE like the bzip2 pipeline. Difficulty: Advanced Topics: transforms, suffix arrays Estimated LOC: 700 Libraries: stdlib.h

500. gzip File Reader/Writer Description: Read and write .gz files (header + DEFLATE). Difficulty: Advanced Topics: gzip format, CRC32 Estimated LOC: 800 Libraries: (self-built DEFLATE)

501. ZIP Archive Reader/Writer Description: Create and extract ZIP archives with stored/deflated entries. Difficulty: Advanced Topics: ZIP format, CRC, compression Estimated LOC: 900 Libraries: zlib

502. Delta Encoding Tool Description: Compute and apply binary diffs between file versions. Difficulty: Intermediate Topics: diffing, patching Estimated LOC: 500 Libraries: stdlib.h

503. Image-Specific Compressor Description: Compress images with prediction + entropy coding (PNG-like). Difficulty: Advanced Topics: filters, entropy coding Estimated LOC: 700 Libraries: stb_image

504. Dictionary Compression Benchmark Description: Compare RLE/Huffman/LZ ratios and speeds on datasets. Difficulty: Intermediate Topics: benchmarking, compression Estimated LOC: 400 Libraries: time.h

505. Streaming Compressor (chunked) Description: Compress unbounded streams with framing and flushing. Difficulty: Advanced Topics: streaming, framing Estimated LOC: 600 Libraries: zlib

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24. Database Systems (506–524)

506. Key-Value Store (in-memory) Description: A hash-backed KV store with get/set/delete. Difficulty: Intermediate Topics: hashing, APIs Estimated LOC: 400 Libraries: stdlib.h

507. Persistent KV Store (log-structured) Description: Append-only log KV store with compaction (Bitcask-style). Difficulty: Advanced Topics: WAL, indexing, compaction Estimated LOC: 700 Libraries: stdio.h

508. LSM-Tree Storage Engine Description: MemTable + SSTables with merges like LevelDB. Difficulty: Advanced Topics: LSM trees, compaction Estimated LOC: 1200 Libraries: stdlib.h

509. B-Tree Disk Index Description: On-disk B+tree supporting inserts and range scans. Difficulty: Advanced Topics: paging, B-trees Estimated LOC: 1000 Libraries: stdio.h

510. Write-Ahead Log & Recovery Description: Durable WAL with crash recovery and checkpoints. Difficulty: Advanced Topics: durability, recovery Estimated LOC: 600 Libraries: fsync

511. SQL Query Parser Description: Parse a subset of SQL into an AST. Difficulty: Advanced Topics: lexing, parsing Estimated LOC: 800 Libraries: stdlib.h

512. Mini SQL Database Engine Description: Parse, plan, and execute SELECT/INSERT with a storage engine. Difficulty: Advanced Topics: databases, execution Estimated LOC: 2000 Libraries: stdlib.h

513. Query Optimizer (cost-based) Description: Reorder joins and choose indexes by estimated cost. Difficulty: Advanced Topics: optimization, statistics Estimated LOC: 800 Libraries: stdlib.h

514. Buffer Pool / Page Cache Manager Description: Cache disk pages with LRU/clock eviction and dirty flushing. Difficulty: Advanced Topics: caching, paging Estimated LOC: 600 Libraries: stdio.h

515. Transaction Manager (MVCC) Description: Provide snapshot isolation with multi-version records. Difficulty: Advanced Topics: MVCC, isolation Estimated LOC: 900 Libraries: stdlib.h

516. Time-Series Database Description: Ingest and query timestamped metrics with downsampling. Difficulty: Advanced Topics: storage, aggregation Estimated LOC: 900 Libraries: stdlib.h

517. Document Store (JSON) Description: Store, index, and query JSON documents by field. Difficulty: Advanced Topics: JSON, indexing Estimated LOC: 900 Libraries: (self-built JSON)

518. Graph Database (basic) Description: Store nodes/edges and run traversal queries. Difficulty: Advanced Topics: graphs, storage Estimated LOC: 900 Libraries: stdlib.h

519. Inverted Index Search Engine Description: Index documents and rank results with TF-IDF. Difficulty: Advanced Topics: indexing, ranking Estimated LOC: 800 Libraries: stdlib.h

520. Columnar Storage Engine Description: Store data by column with compression and vectorized scans. Difficulty: Advanced Topics: column stores, compression Estimated LOC: 800 Libraries: stdlib.h

521. Redis-lite Server Description: Serve GET/SET/LPUSH over the RESP protocol via sockets. Difficulty: Advanced Topics: networking, data structures Estimated LOC: 1000 Libraries: sys/socket.h

522. Bloom-Filter-Backed Cache Description: Avoid disk lookups for absent keys with a Bloom filter. Difficulty: Intermediate Topics: probabilistic structures Estimated LOC: 500 Libraries: stdlib.h

523. Replication & Log Shipping Description: Replicate a KV store to a follower over the network. Difficulty: Advanced Topics: replication, networking Estimated LOC: 800 Libraries: sys/socket.h

524. Database CLI & REPL Description: Interactive client to run queries against your engine. Difficulty: Intermediate Topics: REPL, parsing Estimated LOC: 400 Libraries: readline

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25. Compilers, Interpreters & Virtual Machines (525–553)

525. Reverse Polish (RPN) Calculator VM Description: Evaluate postfix expressions on a small stack machine. Difficulty: Beginner Topics: stacks, evaluation Estimated LOC: 250 Libraries: stdlib.h

526. Tokenizer / Lexer Library Description: Reusable lexer producing tokens with positions. Difficulty: Intermediate Topics: lexing, state machines Estimated LOC: 400 Libraries: stdlib.h

527. Recursive Descent Expression Parser Description: Parse arithmetic into an AST with precedence. Difficulty: Intermediate Topics: parsing, ASTs Estimated LOC: 400 Libraries: stdlib.h

528. Pratt Parser Description: Parse expressions with a Pratt (precedence-climbing) parser. Difficulty: Intermediate Topics: parsing Estimated LOC: 400 Libraries: stdlib.h

529. Brainfuck Interpreter & Optimizer Description: Run Brainfuck with loop-collapsing optimizations. Difficulty: Beginner Topics: interpreters, tape machines Estimated LOC: 300 Libraries: stdio.h

530. Brainfuck-to-C Compiler Description: Transpile Brainfuck into compilable C. Difficulty: Intermediate Topics: code generation Estimated LOC: 300 Libraries: stdio.h

531. Lisp / Scheme Interpreter Description: Parse S-expressions and evaluate with closures. Difficulty: Advanced Topics: interpreters, environments Estimated LOC: 1000 Libraries: stdlib.h

532. Forth Interpreter Description: A threaded, stack-based Forth with a dictionary. Difficulty: Advanced Topics: stack VMs, dictionaries Estimated LOC: 800 Libraries: stdlib.h

533. Tree-Walking Scripting Language Description: Full language with variables, functions, and control flow. Difficulty: Advanced Topics: interpreters, scoping Estimated LOC: 1500 Libraries: stdlib.h

534. Bytecode Compiler & VM Description: Compile a language to bytecode and run it on a VM. Difficulty: Advanced Topics: bytecode, stack VMs Estimated LOC: 2000 Libraries: stdlib.h

535. Register-Based Virtual Machine Description: A register VM with an instruction set and assembler. Difficulty: Advanced Topics: VM design, ISA Estimated LOC: 1200 Libraries: stdlib.h

536. Stack-Based Bytecode Assembler Description: Assemble textual mnemonics into VM bytecode. Difficulty: Intermediate Topics: assembling, encoding Estimated LOC: 500 Libraries: stdlib.h

537. Garbage-Collected Language Runtime Description: Add tracing GC to your interpreter's objects. Difficulty: Advanced Topics: GC, runtimes Estimated LOC: 800 Libraries: stdlib.h

538. Static Type Checker Description: Infer/check types for a small language before running. Difficulty: Advanced Topics: type systems, inference Estimated LOC: 900 Libraries: stdlib.h

539. C Subset Compiler to Assembly Description: Compile a C subset to x86-64 assembly. Difficulty: Advanced Topics: codegen, calling conventions Estimated LOC: 3000 Libraries: stdlib.h

540. JSON Query Language (JQ-lite) Description: Evaluate a path/filter language over JSON. Difficulty: Advanced Topics: parsing, evaluation Estimated LOC: 800 Libraries: (self-built JSON)

541. Regular Expression Compiler to NFA/DFA Description: Compile regexes to automata and match with them. Difficulty: Advanced Topics: automata, compilation Estimated LOC: 700 Libraries: stdlib.h

542. Calculator Language with JIT (dynasm-free) Description: Emit machine code for expressions and execute it. Difficulty: Advanced Topics: JIT, machine code Estimated LOC: 700 Libraries: sys/mman.h

543. Peephole Optimizer Description: Apply local optimizations to a bytecode/IR stream. Difficulty: Advanced Topics: optimization Estimated LOC: 500 Libraries: stdlib.h

544. Constant Folding & Dead Code Elimination Description: Simplify an AST/IR before code generation. Difficulty: Advanced Topics: optimization, IR Estimated LOC: 500 Libraries: stdlib.h

545. SSA IR Builder Description: Convert a control-flow graph into SSA form. Difficulty: Advanced Topics: compiler IR, dominance Estimated LOC: 900 Libraries: stdlib.h

546. Register Allocator (graph coloring) Description: Allocate registers by coloring an interference graph. Difficulty: Advanced Topics: graph coloring, compilers Estimated LOC: 700 Libraries: stdlib.h

547. Parser Generator (mini-yacc) Description: Generate a parser from a grammar specification. Difficulty: Advanced Topics: LR/LL parsing, codegen Estimated LOC: 1200 Libraries: stdlib.h

548. Lexer Generator (mini-lex) Description: Generate a scanner from regex rules. Difficulty: Advanced Topics: automata, codegen Estimated LOC: 900 Libraries: stdlib.h

549. Template/Macro Preprocessor (cpp-lite) Description: Implement #include, #define, and conditionals. Difficulty: Advanced Topics: preprocessing, macros Estimated LOC: 800 Libraries: stdlib.h

550. Query Language for CSV (SQL-on-files) Description: Run SELECT/WHERE/GROUP BY over CSV files. Difficulty: Advanced Topics: parsing, execution Estimated LOC: 900 Libraries: stdlib.h

551. WebAssembly Interpreter (subset) Description: Parse and execute a subset of WASM bytecode. Difficulty: Advanced Topics: bytecode, stack VMs Estimated LOC: 1500 Libraries: stdlib.h

552. Markup Language Compiler (config DSL) Description: Compile a custom DSL into a runtime config structure. Difficulty: Advanced Topics: DSLs, parsing Estimated LOC: 700 Libraries: stdlib.h

553. Interactive Language REPL with Errors Description: A REPL with helpful error messages and line editing. Difficulty: Advanced Topics: interpreters, UX Estimated LOC: 700 Libraries: readline

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26. Emulators (554–566)

554. CHIP-8 Emulator Description: Emulate the CHIP-8 virtual machine and run ROMs. Difficulty: Intermediate Topics: opcode decoding, emulation Estimated LOC: 700 Libraries: SDL2

555. Intel 8080 CPU Emulator Description: Emulate the 8080 and run Space Invaders. Difficulty: Advanced Topics: CPU emulation Estimated LOC: 1500 Libraries: SDL2

556. MOS 6502 CPU Emulator Description: Cycle-accurate 6502 emulator with a test suite. Difficulty: Advanced Topics: CPU emulation, cycles Estimated LOC: 1800 Libraries: none

557. NES Emulator (subset) Description: Emulate 6502 + PPU to run simple NES games. Difficulty: Advanced Topics: emulation, graphics Estimated LOC: 4000 Libraries: SDL2

558. Game Boy Emulator (subset) Description: Emulate the LR35902 CPU and render the LCD. Difficulty: Advanced Topics: emulation, timing Estimated LOC: 5000 Libraries: SDL2

559. Z80 CPU Emulator Description: Emulate the Z80 for retro-computer targets. Difficulty: Advanced Topics: CPU emulation Estimated LOC: 2000 Libraries: none

560. Simple RISC-V (RV32I) Emulator Description: Execute RV32I instructions and run compiled ELF. Difficulty: Advanced Topics: ISA emulation, ELF Estimated LOC: 1500 Libraries: elf.h

561. Fantasy Console (PICO-8-like) Description: A tiny virtual console with a scripting API and display. Difficulty: Advanced Topics: VM, graphics, scripting Estimated LOC: 2500 Libraries: SDL2

562. Assembler for Your Emulated CPU Description: Assemble source into ROMs for your emulator. Difficulty: Intermediate Topics: assembling Estimated LOC: 600 Libraries: stdlib.h

563. Terminal (VT100) Emulator Description: Interpret ANSI/VT100 escape sequences into a screen buffer. Difficulty: Advanced Topics: terminal protocols, pty Estimated LOC: 1200 Libraries: SDL2, pty.h

564. Simple GPU / Blitter Simulator Description: Model a 2D blitter with sprites and layers. Difficulty: Advanced Topics: hardware modeling Estimated LOC: 700 Libraries: SDL2

565. Retro Sound Chip Emulator (AY/SID-like) Description: Emulate a programmable sound generator and play tunes. Difficulty: Advanced Topics: audio synthesis, emulation Estimated LOC: 800 Libraries: SDL2

566. Debugger for Your Emulator Description: Step, breakpoint, and inspect memory/registers of an emulated CPU. Difficulty: Advanced Topics: debugging, emulation Estimated LOC: 700 Libraries: ncurses

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27. Embedded, IoT & Robotics (567–590)

567. GPIO Blink & Button (Raspberry Pi) Description: Blink an LED and read a button via sysfs/gpiod. Difficulty: Beginner Topics: GPIO, embedded I/O Estimated LOC: 200 Libraries: libgpiod

568. PWM LED Dimmer / Servo Driver Description: Control LED brightness and servo angle with PWM. Difficulty: Intermediate Topics: PWM, timing Estimated LOC: 250 Libraries: pigpio

569. I2C Sensor Reader Description: Read temperature/humidity from an I2C sensor. Difficulty: Intermediate Topics: I2C, protocols Estimated LOC: 300 Libraries: linux/i2c-dev.h

570. SPI Device Driver (userspace) Description: Communicate with an SPI display or ADC. Difficulty: Intermediate Topics: SPI, protocols Estimated LOC: 350 Libraries: linux/spi/spidev.h

571. UART Serial Communication Description: Send/receive framed data over a serial port. Difficulty: Intermediate Topics: serial, termios Estimated LOC: 350 Libraries: termios.h

572. Bare-Metal Blinky (STM32/AVR) Description: Toggle a pin with no OS by writing registers directly. Difficulty: Advanced Topics: registers, freestanding Estimated LOC: 200 Libraries: CMSIS / avr-libc

573. Bare-Metal UART Driver Description: Implement UART TX/RX by poking peripheral registers. Difficulty: Advanced Topics: MMIO, drivers Estimated LOC: 350 Libraries: none (freestanding)

574. RTOS Task Scheduler (bare-metal) Description: Cooperative/preemptive scheduler for a microcontroller. Difficulty: Advanced Topics: context switching, timers Estimated LOC: 600 Libraries: CMSIS

575. Ring Buffer for ISR Data Description: Interrupt-safe buffer for streaming sensor data. Difficulty: Intermediate Topics: ISRs, buffers Estimated LOC: 250 Libraries: none (freestanding)

576. Debounce & Input State Machine Description: Debounce buttons and detect long/short presses. Difficulty: Intermediate Topics: state machines, timing Estimated LOC: 250 Libraries: none

577. PID Motor Controller Description: Control motor speed/position with a tuned PID loop. Difficulty: Advanced Topics: control theory, PID Estimated LOC: 400 Libraries: none

578. Line-Following Robot Logic Description: Steer a robot using IR sensor input and PID. Difficulty: Advanced Topics: robotics, control Estimated LOC: 450 Libraries: pigpio

579. Ultrasonic Distance Radar Description: Map distances with an ultrasonic sensor on a servo. Difficulty: Intermediate Topics: sensors, timing Estimated LOC: 400 Libraries: pigpio

580. IMU Sensor Fusion (complementary filter) Description: Fuse accelerometer/gyro data into stable orientation. Difficulty: Advanced Topics: sensor fusion, math Estimated LOC: 450 Libraries: linux/i2c-dev.h

581. MQTT Client (from scratch) Description: Publish/subscribe to an MQTT broker over TCP. Difficulty: Advanced Topics: MQTT protocol, networking Estimated LOC: 700 Libraries: sys/socket.h

582. CoAP Client/Server Description: Implement constrained-device messaging over UDP. Difficulty: Advanced Topics: CoAP, UDP Estimated LOC: 700 Libraries: sys/socket.h

583. Home Automation Hub Description: Aggregate sensors and expose control via a REST API. Difficulty: Advanced Topics: IoT, HTTP, devices Estimated LOC: 1000 Libraries: sys/socket.h

584. OTA Firmware Updater Description: Download and flash firmware with rollback safety. Difficulty: Advanced Topics: flashing, integrity Estimated LOC: 700 Libraries: OpenSSL

585. Modbus RTU/TCP Master Description: Poll industrial devices over Modbus. Difficulty: Advanced Topics: Modbus, protocols Estimated LOC: 600 Libraries: termios.h

586. Data Logger to SD/Flash Description: Log timestamped sensor data with wear-friendly writes. Difficulty: Intermediate Topics: storage, timing Estimated LOC: 400 Libraries: stdio.h

587. Low-Power Sleep Scheduler Description: Duty-cycle a device between sleep and sampling. Difficulty: Advanced Topics: power management, timers Estimated LOC: 350 Libraries: none (freestanding)

588. Robot Kinematics Solver Description: Compute forward/inverse kinematics for a robot arm. Difficulty: Advanced Topics: robotics, linear algebra Estimated LOC: 600 Libraries: math.h

589. CAN Bus Message Decoder Description: Read and decode CAN frames on a vehicle bus. Difficulty: Advanced Topics: CAN, protocols Estimated LOC: 500 Libraries: linux/can.h

590. Bootloader with Firmware Verification Description: A small bootloader that verifies and jumps to signed firmware. Difficulty: Advanced Topics: bootloaders, crypto Estimated LOC: 600 Libraries: (self-built crypto)

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28. Artificial Intelligence & Machine Learning (591–611)

591. Perceptron & Logistic Regression Description: Train a linear classifier with gradient descent. Difficulty: Intermediate Topics: ML basics, gradients Estimated LOC: 350 Libraries: math.h

592. K-Nearest Neighbors Classifier Description: Classify points by nearest labeled neighbors. Difficulty: Beginner Topics: distance metrics Estimated LOC: 300 Libraries: math.h

593. K-Means Clustering Description: Cluster data with Lloyd's algorithm and visualization. Difficulty: Intermediate Topics: clustering Estimated LOC: 400 Libraries: math.h

594. Decision Tree Learner Description: Build classification trees using information gain. Difficulty: Intermediate Topics: trees, entropy Estimated LOC: 500 Libraries: math.h

595. Naive Bayes Text Classifier Description: Classify documents (e.g. spam) with Naive Bayes. Difficulty: Intermediate Topics: probability, NLP Estimated LOC: 450 Libraries: stdlib.h

596. Feedforward Neural Network Description: Train an MLP with backpropagation on MNIST. Difficulty: Advanced Topics: neural networks, backprop Estimated LOC: 700 Libraries: math.h

597. Autograd / Tensor Engine (micro) Description: Reverse-mode automatic differentiation over a tensor graph. Difficulty: Advanced Topics: autodiff, graphs Estimated LOC: 800 Libraries: math.h

598. Convolutional Neural Network Description: Implement conv/pool layers and train an image classifier. Difficulty: Advanced Topics: CNNs, convolution Estimated LOC: 1200 Libraries: math.h

599. Recurrent Network / LSTM Description: Train an RNN/LSTM for character-level text generation. Difficulty: Advanced Topics: sequence models Estimated LOC: 1000 Libraries: math.h

600. Linear SVM (SGD) Description: Train a support vector machine with hinge loss. Difficulty: Advanced Topics: optimization, ML Estimated LOC: 500 Libraries: math.h

601. Q-Learning Agent Description: Learn to solve gridworld/CartPole via tabular Q-learning. Difficulty: Intermediate Topics: reinforcement learning Estimated LOC: 450 Libraries: stdlib.h

602. Minimax + Alpha-Beta Game AI Description: A reusable adversarial search engine for board games. Difficulty: Advanced Topics: game trees, pruning Estimated LOC: 500 Libraries: stdlib.h

603. Monte Carlo Tree Search Description: Implement MCTS for games like Connect Four/Go-lite. Difficulty: Advanced Topics: search, simulation Estimated LOC: 600 Libraries: math.h

604. Genetic Programming Evolver Description: Evolve programs/expressions to fit target functions. Difficulty: Advanced Topics: evolutionary computation Estimated LOC: 700 Libraries: stdlib.h

605. N-Gram Language Model Description: Train and sample from an n-gram model for text. Difficulty: Intermediate Topics: NLP, probability Estimated LOC: 400 Libraries: stdlib.h

606. Recommendation Engine (collaborative filtering) Description: Recommend items using matrix factorization. Difficulty: Advanced Topics: linear algebra, ML Estimated LOC: 600 Libraries: math.h

607. Principal Component Analysis Description: Reduce dimensionality via eigen-decomposition. Difficulty: Advanced Topics: linear algebra Estimated LOC: 500 Libraries: math.h

608. Simple Neural Net Inference Engine Description: Load trained weights and run inference (no training). Difficulty: Intermediate Topics: inference, matrices Estimated LOC: 400 Libraries: math.h

609. Handwritten Digit Recognizer (end-to-end) Description: Train and demo a digit classifier with a drawing UI. Difficulty: Advanced Topics: ML, GUI integration Estimated LOC: 1000 Libraries: math.h, SDL2

610. Anomaly Detector (statistical) Description: Flag outliers in streams via z-score/EWMA. Difficulty: Intermediate Topics: statistics, streaming Estimated LOC: 350 Libraries: math.h

611. Tiny Tensor Library (BLAS-lite) Description: N-dim arrays with broadcasting and matmul for ML. Difficulty: Advanced Topics: tensors, numerical computing Estimated LOC: 900 Libraries: math.h

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29. Parsers & Serialization (612–627)

612. Binary Serialization Library Description: Serialize/deserialize structs to a compact binary format. Difficulty: Intermediate Topics: serialization, endianness Estimated LOC: 400 Libraries: stdint.h

613. Protocol Buffers Decoder (subset) Description: Decode protobuf wire format into fields. Difficulty: Advanced Topics: varints, wire formats Estimated LOC: 500 Libraries: stdint.h

614. MessagePack Codec Description: Encode/decode the MessagePack binary format. Difficulty: Intermediate Topics: serialization Estimated LOC: 500 Libraries: stdint.h

615. YAML Parser (subset) Description: Parse a practical subset of YAML into a value tree. Difficulty: Advanced Topics: parsing, indentation Estimated LOC: 800 Libraries: stdlib.h

616. TOML Parser Description: Parse TOML config files into typed values. Difficulty: Advanced Topics: parsing Estimated LOC: 700 Libraries: stdlib.h

617. XML Parser & DOM Description: Parse XML into a navigable DOM tree. Difficulty: Advanced Topics: parsing, trees Estimated LOC: 800 Libraries: stdlib.h

618. CSV ↔ JSON ↔ YAML Converter Description: Convert data between common formats. Difficulty: Intermediate Topics: parsing, serialization Estimated LOC: 600 Libraries: (self-built parsers)

619. Bencode (BitTorrent) Codec Description: Encode/decode bencoded data. Difficulty: Intermediate Topics: serialization Estimated LOC: 350 Libraries: stdlib.h

620. ASN.1 / DER Decoder (subset) Description: Parse DER-encoded structures (e.g. certificates). Difficulty: Advanced Topics: TLV parsing Estimated LOC: 700 Libraries: stdint.h

621. S-Expression Parser Description: Parse and print Lisp-style S-expressions. Difficulty: Intermediate Topics: parsing, trees Estimated LOC: 400 Libraries: stdlib.h

622. Schema Validator Description: Validate JSON documents against a schema. Difficulty: Advanced Topics: validation, recursion Estimated LOC: 700 Libraries: (self-built JSON)

623. Config Reload & Hot-Swap Library Description: Watch and safely reload config without restart. Difficulty: Intermediate Topics: parsing, inotify Estimated LOC: 400 Libraries: sys/inotify.h

624. URL & Query String Parser Description: Parse and build URLs with percent-encoding. Difficulty: Beginner Topics: parsing, encoding Estimated LOC: 300 Libraries: stdlib.h

625. HTTP Header & MIME Parser Description: Robustly parse headers, tokens, and MIME types. Difficulty: Intermediate Topics: parsing, HTTP Estimated LOC: 400 Libraries: stdlib.h

626. Log Format Parser (Apache/nginx) Description: Parse access logs into structured records for analysis. Difficulty: Intermediate Topics: parsing, regex Estimated LOC: 400 Libraries: regex.h

627. Binary Grammar / Kaitai-style Reader Description: Describe a binary format declaratively and parse it. Difficulty: Advanced Topics: DSLs, binary parsing Estimated LOC: 800 Libraries: stdlib.h

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30. Developer Tools (628–648)

628. Argument Parser Library (getopt++) Description: Declarative CLI parsing with subcommands and help text. Difficulty: Intermediate Topics: CLI design, parsing Estimated LOC: 500 Libraries: stdlib.h

629. Logging Framework (levels/sinks) Description: Structured logging with levels, sinks, and formatting. Difficulty: Intermediate Topics: logging, design Estimated LOC: 450 Libraries: stdio.h

630. Config Management Library Description: Layer defaults, files, env, and flags into one config. Difficulty: Intermediate Topics: config, precedence Estimated LOC: 450 Libraries: stdlib.h

631. Hot-Reload File Watcher for Dev Description: Rebuild/restart a target when source files change. Difficulty: Intermediate Topics: inotify, subprocess Estimated LOC: 400 Libraries: sys/inotify.h

632. Code Line Counter (cloc-lite) Description: Count code/comment/blank lines by language. Difficulty: Intermediate Topics: parsing, stats Estimated LOC: 450 Libraries: dirent.h

633. Dependency Graph Visualizer Description: Parse #include graphs and export to DOT/Graphviz. Difficulty: Intermediate Topics: parsing, graphs Estimated LOC: 450 Libraries: stdlib.h

634. Code Formatter (C) Description: Reformat C source with configurable style rules. Difficulty: Advanced Topics: lexing, formatting Estimated LOC: 800 Libraries: stdlib.h

635. Static Analyzer / Linter (C) Description: Flag common bugs (unused vars, null derefs) via AST checks. Difficulty: Advanced Topics: static analysis, parsing Estimated LOC: 1000 Libraries: stdlib.h

636. Documentation Generator (Doxygen-lite) Description: Extract doc comments and emit HTML/Markdown docs. Difficulty: Intermediate Topics: parsing, output Estimated LOC: 600 Libraries: stdlib.h

637. Benchmark Harness Library Description: Time functions, warm up, and report stable statistics. Difficulty: Intermediate Topics: benchmarking, statistics Estimated LOC: 400 Libraries: time.h

638. Crash Reporter (backtrace on signal) Description: Catch faults and print a symbolized stack trace. Difficulty: Advanced Topics: signals, backtrace Estimated LOC: 400 Libraries: execinfo.h

639. Assertion & Contract Library Description: Rich assertions with messages and optional contracts. Difficulty: Intermediate Topics: macros, debugging Estimated LOC: 300 Libraries: stdio.h

640. Diff & Patch Toolkit Description: Generate unified diffs and apply patches to files. Difficulty: Advanced Topics: diffing, patching Estimated LOC: 700 Libraries: stdlib.h

641. Code Search Tool (ack/ag-lite) Description: Fast recursive code search respecting ignore files. Difficulty: Intermediate Topics: search, traversal Estimated LOC: 500 Libraries: regex.h

642. Environment Diff Tool Description: Compare environment/config between two setups. Difficulty: Beginner Topics: parsing, diffing Estimated LOC: 300 Libraries: stdlib.h

643. TODO/FIXME Scanner Description: Aggregate code annotations into a report/board. Difficulty: Beginner Topics: scanning, reporting Estimated LOC: 300 Libraries: dirent.h

644. Macro Expansion Explorer Description: Show how C macros expand step by step. Difficulty: Advanced Topics: preprocessing Estimated LOC: 600 Libraries: stdlib.h

645. Command Palette / Fuzzy Finder (fzf-lite) Description: Interactive fuzzy filter over piped input. Difficulty: Intermediate Topics: fuzzy matching, ncurses Estimated LOC: 500 Libraries: ncurses

646. Code Metrics / Complexity Analyzer Description: Compute cyclomatic complexity per function. Difficulty: Advanced Topics: static analysis Estimated LOC: 600 Libraries: stdlib.h

647. Snippet Manager CLI Description: Store, tag, search, and paste code snippets. Difficulty: Intermediate Topics: storage, search Estimated LOC: 450 Libraries: stdlib.h

648. Interactive Regex Tester Description: Live-test regexes against sample text with highlighting. Difficulty: Intermediate Topics: regex, ncurses Estimated LOC: 450 Libraries: regex.h, ncurses

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31. Git-like Tools, Build Systems, Testing, Profilers & Debuggers (649–660)

649. Content-Addressable Store (Git objects) Description: Store blobs/trees/commits by SHA-1 like Git's object DB. Difficulty: Advanced Topics: hashing, storage Estimated LOC: 600 Libraries: OpenSSL, zlib

650. Mini Version Control System (git-lite) Description: init, add, commit, log, checkout with a real object model. Difficulty: Advanced Topics: VCS internals, hashing Estimated LOC: 1500 Libraries: OpenSSL, zlib

651. Diff-Based Branching & Merge Description: Add branches and three-way merges to your mini-VCS. Difficulty: Advanced Topics: merging, diff algorithms Estimated LOC: 900 Libraries: (self-built diff)

652. Build System (make-lite) Description: Parse rules, resolve dependencies, and rebuild stale targets. Difficulty: Advanced Topics: DAGs, timestamps, exec Estimated LOC: 800 Libraries: sys/stat.h

653. Incremental Build Cache Description: Cache build outputs keyed by input hashes (ccache-style). Difficulty: Advanced Topics: hashing, caching Estimated LOC: 600 Libraries: OpenSSL

654. Task Runner / Job Orchestrator Description: Run task graphs in parallel respecting dependencies. Difficulty: Advanced Topics: DAGs, concurrency Estimated LOC: 700 Libraries: pthread

655. Unit Test Framework Description: Test registration, assertions, fixtures, and TAP output. Difficulty: Intermediate Topics: macros, reporting Estimated LOC: 500 Libraries: stdio.h

656. Mocking / Stubbing Library Description: Replace functions with mocks and verify call expectations. Difficulty: Advanced Topics: linker tricks, function pointers Estimated LOC: 500 Libraries: stdlib.h

657. Code Coverage Tool Description: Instrument source to report line/branch coverage. Difficulty: Advanced Topics: instrumentation, parsing Estimated LOC: 800 Libraries: stdlib.h

658. Sampling Profiler Description: Periodically sample the stack to build a flame profile. Difficulty: Advanced Topics: signals, backtrace, stats Estimated LOC: 600 Libraries: execinfo.h

659. Instrumenting Profiler Description: Time function entry/exit via -finstrument-functions hooks. Difficulty: Advanced Topics: instrumentation, timing Estimated LOC: 500 Libraries: time.h

660. Full-Featured Debugger (ptrace + DWARF) Description: Source-level breakpoints and variable inspection using DWARF. Difficulty: Advanced Topics: ptrace, DWARF, debugging Estimated LOC: 2000 Libraries: sys/ptrace.h, libdwarf

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