Version 1.2

Changelog:
- Adjusted level 16
- Adjusted level 18
- Adjusted level Bottom
- Fixed certain objects not returning on undo
- Fixed a massive slowdown when detonating bombs in certain circumstances
- Added more tooltips about checkpoints, restarting etc
- Fixed the gem counter getting desynced when undoing
- Fixed the gem counter indicating that a level is unbeatable even after undoing
- Made a particular memory-related bug less common but haven't fixed it fully yet