I became obsessed with retro games and wanted to program some games of my own. I target Z80 as one of the most used CPU for retro games.
Website tutorial for the Z80: https://benjamin.computer/posts/2022-04-22-ZX-coding.html
VASM: http://www.compilers.de/vasm.html
Z80 instruction set: https://en.wikipedia.org/wiki/Zilog_Z80#Z80_assembly_language
General tutorials and help material: https://www.assemblytutorial.com/z80/
Very helpful Github repo: https://github.com/Z80-Retro