Arrow keys are default movement type. During play, you can go ahead and switch between modes at will (don't worry, if you're using mouse and in a tight spot and need to switch to arrows, clicking the "arrows" button won't move you). Avoid the red squares while collecting the black squares. Every time you collect a black square your score goes up but you also get bigger and another red square spawns. The blue powerup sets your size back to the original, while the pink powerup clears all the cloned red squares from the screen.
All feedback appreciated. It's been ages since I've last actually used Scratch so I'm sort of relearning everything as I go but I really enjoy doing this and I hope I can make something that at least one person will enjoy. Update 8/21/15 -Fixed the cloning issue! Now there will only be one new red square for each time you collect a black square, instead of the number doubling each time. Update 8/22/15 -Tried to fix a bunch of issues, but none of the fixes worked. Currently having problems with squares spawning on top of the circle or each other, making it impossible to collect the black ones or automatically ending the game. -Made the arrow keys less sensitive, so the circle doesn't move as far when you just give a little tap. -Added powerups