Someone please ELI5. I was no savant at 13 years old. But I remember being able to trace through 65C02 code and figure out enough of it to hack around and fix Software Automated Mouth to work in 80 column mode. When you redirected output from SAM to the screen it would revert to 40 column mode.
I remember also hacking around with other 65C02 assembly language applications and making modifications.
Over the next 10 years, I worked with other processors in assembly (68K, PPC, x86) and 65C02 was simple. Especially since most programs were written in 65C02 and not compiled down to it.
I think what helped most was that programs were small and that no tricks were necessary or even possible to be efficient w.r.t. cache misses.
If Linux ran on some multi-gigahertz 64-bit evolution of the 6502 the instruction set would still be simple, but a few Gigabytes of 6502 code still would be a challenge to understand, more so if that 6502 were out of order, speculatively executing, multi-core, and various parts of the code were written taking that into account.
Later on, I ported it to work with ProDOS.
https://en.wikipedia.org/wiki/Software_Automatic_Mouth
I remember also hacking around with other 65C02 assembly language applications and making modifications.
Over the next 10 years, I worked with other processors in assembly (68K, PPC, x86) and 65C02 was simple. Especially since most programs were written in 65C02 and not compiled down to it.