Grey Matter is an anti-shooter, which means that you can't actually shoot. You are the bullet, and you attack by directly colliding with the exposed brain-meats of your enemies. It looks great and sounds even better. The gameplay has all the depth of a modern professional shoot-'em-up, thanks to the combo system. Grey-Matter is perfectly playable without using the Trinity Attacks, but if you do employ them, it becomes almost like a hyperactive, twitchy puzzle game.