Update 4 - Coop Mode

Update 4:
- Added a coop option for the Normal and Hard gamemodes, the enemies will only target player 1 but player 2 can still die if they get in the way of enemies. If player 2 dies, they will revive after 15 seconds, but only if player 1 doesn't die before that!.
- Added a new music piece "Time for a Hell Wicked Dance" for the main menu.
- Fixed being able to camp on corners.
- Fixed many issues related to points, time, buttons, and the player.