A decent shooter, though the enemy variety is very lacking because only A to D fights you. Missed opportunity for A to be a rocket that can explode on impact. B is just a slower version of C, and D goes within a straight line, stops, then goes again. More enemies could be fun, but unless you have a good grasp on programming, these ideas can go to ruin by bad execution, like X being the enemy that zips across the screen diagonally, or Z striking R in a Z-line. L could shoot back or U could deflect bullets.