DoctorWkt/acwj ? reverse-engineered prompt

Build me a practical little compiler in C that can compile a useful subset of C and grow step by step, with clear explanations along the way.

I want it to start with scanning and parsing, then handle expressions, statements, variables, functions, pointers, arrays, structs, enums, typedefs, and a basic preprocessor. It should generate real assembly or another simple backend so I can actually compile and run test programs, and it would be great if it can target more than one platform later. Please also include a simple regression test setup so I can check that each new language feature still works as I add it.

Keep it educational and easy to follow, like a hands on compiler writing journey, not an abstract theory project. If you need to look up current docs or backend details online, go ahead.