Added Gravity Manipulation!

Just updated my game Beat Blast with a few changes!

• New level: Amiga (really fun, but i think i made it too hard)
• Added gravity and gravity switching
• You can now see you best percentage on a level in main menu
• Tweaks n' fixes

This is probably as much as I'm gonna get to for the game jam but I might come back and add some more stuff, who knows?