[RetroSpark]

It doesn't sound like they include the entire ROM, only the parts necessary to play back the recording. If you "take control", the game may try to access parts of the ROM which are missing, which causes the quote to reset. This happens frequently with the Metroid II example - the Tetris one seems much more robust.

[jf]

Exactly right! Part of a quote is a "ROM validity mask" which is checked on each memory access. When an "invalid" memory address is requested, we'll fire a callback which in this case just resets the game.

The durability of each quote depends on the actions taken while the quote was being made. In the quote of Metroid II, for example, many of the sprites were not recorded, so unless you do exactly what was done in the recording, you'll get a reset.

Here's a visualization of the Metroid II quote: https://tenmile.quote.games/quote-visualizer.html#drop=https...