I have a suggestion to edit level 11-A to add more space in the top left. This is because undo savestates aren’t recorded when you’re in aura range of a door, and it’s really annoying when undoing puts you back way too much when you make a mistake. Something like this would work: (the screenshot was made with Undertale Mod Tool)
https://img.itch.zone/aW1nLzI3MjYyOTUyLnBuZw==/original/jmL7%2FT.png
