A ship that fires bullets

Classic Alien Invasion, player conrols a ship front stage and center. The ship can move left and right and fire bullets. The goal is to shoot down the continual flow of alien invaders that appear at the top of the screen making there way down to the bottom. If any alien touches the players ship or makes it to the bottom of the screen the player loses a ship. When the player has lost 3 ships the game is over.