New main menu! (and other changes)

Hello guys!

I've uploaded a new small update to the game featuring a new main menu! It's still a work-in-progress, but it's better than before.

Other small changes are:

• Added support for WASD movement
• A new in game phase panel (I'm still working on new sprites to use as phase indicators, for now it's a proof of concept)
• A new player upgrade
• Small fixes to the pathfinding for bigger enemies
• Small fixes to the level generation algorithm
• When trying to move in a direction blocked by something, the character will now face that direction instead of not responding to the input