Yes, me too. This is good to know, but basically it means I can’t rely on old conversations any more. Using a “handoff” file to try and start a new conversation is effectively the same thing as what they did under the hood. So yeah, you can’t rely on old conversations to be as informed when you pick it back up.

I use the carry flag in a lot of z80 assembly for communicating a status of an operation. XOR doesn’t mess with the carry flag, I think it’s another point in favor of xor. (Though I don’t remember even considering using sub)

This is the exact reason I remember from back in the 80's. Perform arithmetic, clear register, CF is still valid.

Then there’s chip8 and a chip8 emulator on the gameboy :) https://github.com/lancekindle/damaged-chip8