Complete Overhaul [v2]

Completely rewritten the entire code, ditching my previous attempt at using a Vector class

There are now five levels in the game!

I do believe there might be an issue with undoing (I've had issues where sometimes pushing a box into another box makes the pushed block move incorrectly). However, with the stress testing I've done, it should not happen. If it does, please leave an issue report with steps to replicate so I can find out how to patch it