I also started as a programmer on a C64. BASIC didn‘t get you very far, so assembly it was. The machine code monitor, all the three letter mnemonics and ??? when it couldn‘t disassemble are fond memories.

When I switched to the PC I had great hopes but outright hated it after a short while. All this restrictions on the registers were confusing. The segment modell even more. And good graphics required programming the VGA cards bitplane modes [1] which still makes me dizzy when I think about it. Wished I had an Amiga.

Programming the 6510 and VIC and SID was so smooth in comparison.

[1] In these modes the bits making up a single pixel where not in the same place. To manipulate a single pixel you had to manipulate several bits in different places of the RAM without affecting the adjacent bits in the respective words. Crazy stuff.