Thanks for the reply. The idea with the undo button is just to let you jump back a few turns in case you hit the wrong button or realise you've gone wrong on one of the puzzles. I played around with the idea of capping the length of the undo but I didn't want to make the game unaccessible to anyone so I left it endless. It's definitely something to consider and maybe I add it as an option in a 'accessible' mode option in the menus going forward.