stage: Space Invaders! (1) +1

I based this stage off of the game Space Invaders; it was a good game, and it makes a pretty decent stage as well. I don't really recommend using CPU's on this stage if items are turned on due to the fact that if an item were to land somewhere near the middle of the stage, the CPU's will go after them at some point. Anyways I hope everybody likes this as much as I do!