I love the projects this person works on, usually full or close to full implementations in very small amounts of code. The one I first learned about was Tiny C

I love the projects this person works on, usually full or close to full implementations in very small amounts of code. The one I first learned about was Tiny C Compiler. It is discontinued now, but it is an about 100K compiler,linker,assembler that can compile many programs like the links browser. https://bellard.org/tcc/ https://bellard.org/tcc/ If that is too large, you can go with the project that inspired it, the Obfuscated Tiny C Compiler, a 2048 byte compiler that supports a subset of C. https://bellard.org/otcc/ https://bellard.org/otcc/ All these projects are great for learning from.