Neat. When I owned 8-bit machines back in the 1980's, I never bothered to learn assembly; just BASIC. I'd love to tinker with retro computers again including things like the Commander X16, but to be honest I'm too old and impatient to code in assembly even though I'm comfy with it now. If I could use a C compiler that inflicted a non-heinous size/performance penalty, I'd be happy. Especially if I could link in asm libs for performance-critical or low-level functions.
Idea ... If you want to stick to a (late) 1980s platform AND you want to code in C without penalty, consider the Sega Genesis.
68000 CPU. There's a mature and helpful homebrew scene. Documentation is good. The SGDK devkit/framework is nice and gives you a no fuss pipeline from C through GCC to a ROM file output that you can run on any emulator, or actual Genesis console (flash cart), or an FPGA like the MiSTer project. 68K assembly is pleasant IMO, if you want to sprinkle in some of that with your C. And, to satisfy an 8-bit itch, the Genesis also has a Z80 CPU on board, typically used for audio programming. Which, by the way, gives you authentic 1980s arcade/console FM synthesis.
IMO the Genesis' architecture of sprites, tilemaps, and palettes is very sane and easy to grok (compared to, say, the Super Nintendo of the era). Also, flat memory model. Yay.
