Excellent game: very addictive and great concept, a simple idea which you have executed very well. Some difficulties I experienced while playing is that, while the splitscreen is a very cool concept, it was difficult to tell where the other player was. This could be solved by zooming the camera out a bit, or adding an arrow that points to the other player's location (this could maybe appear once every 30 seconds or something to make it slightly harder to hide). Also some powerups would be cool: maybe instead of the enemies.