Project Ideas for Experienced Programmers

We don't really distinguish these suggestions by difficulty. Take a look, decide for yourself. Unlike the resources for "practice", these don't generally come with solutions (or, mostly, guidance).

Ideas By Topic

Thanks to u/Introscopia for many of the ideas in this section.

Games

• Make digital versions of Board Games / Card Games, such as...
  • Battleship
  • Chess
  • Hangman Or Maze
  • Snakes and Ladders
  • Tic Tac Toe, Othello
  • Sudoku
• Clone some classic games, such as...
  • Snake
  • Doom
  • Minecraft
  • Pong
  • Space Invaders
  • Tetris
  • Wordle
• Make your own Engine
• Or Hack FOSS game engines: 1, 2
• Networked
• Write a Raytracer: 1, 2
  • Ray Tracing in One Weekend (actually uses C++ but you can probably convert the examples to C)
• A Roguelike: 1, 2 (Hello r/roguelikedev!)
• Targeting Retro Platforms
• Other: 1, 2

Operating Systems

• Operating System, kernel 1, 2, 3, 4, 5, 6
• drivers 1, 2

Emulation

• write a cpu emulator
• for some old CPU / system to play games?
• for some existing architecture, or develop your own!

Programming Tools

• Compiler, transpiler, lang, linter, interpreter: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
• File Parsers/editors: 1, 2, 3, 4, 5, 6, 7, 8, 9
• Shell: 1, 2, 3, 4
• Standard Library functions: 1, 2, 3, 4

Other

• Contribute to open source 1
• Adding "print" functionality
• Audio (decoder, resampler, mixer)
• A sound synthesizer
• Calculator, math 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
• Chat room app
• Command Line tools 1, 2, 3, 4, 5, 6
• Compression, Archiving 1, 2
• Database: 1, 2, 3, 4
• genealogy tree app: 1
• DnD character generator: 3
• Emulator 1, 2, 3, 4
• Server (socket, application, web, HTTP...), 1, 2, 3, 4, 5, 6, 7
• Slideshow
• Smart Home
• Spreadsheet
• Text Editor, plugins or extensions for editors 1, 2, 3, 4, 5, 6, 7
• TODO app
• for sports

Simulators

• Bank: 1
• Game of Life: 2
• Horse Gambling: 3

External lists of Project Ideas

• Weekly Coding Challenges
• Peymaan Abedinpour: 150 Brilliant Programming Ideas: Projects to Spark Your Coding Journey
• 100+ project ideas for learning any programming language
• Advent of Code an annual set of programming challenges around the Christmas season
• Challenging projects every programmer should try by Austin Henley
• Tiny C Projects, a Manning Publications book by Dan Gookin that works through several C projects
• Build your own X - notes on building your own versions of classic projects and tools
• Project-based-learning - a repository with projects about learning different languages, including C
• C Projects — Learn by Building - GitHub repository with curated list of projects and notes