[Someone]

Nice article, but it doesn’t mention the really gnarly stuff such as using the fact that a subroutine happens to return with some flags set, or with some fixed value in the X register to shave of some initialization instruction in the code calling it.

A main advantage of the 6502 is that it only has 64 kilobytes of memory ;-). That means sufficiently advanced and motivated programmers can keep the entire program in their head, and also nudges them to avoid bloat such as the use of 16-bit integers.