Space Invaders (dk'tronics)

Space Invaders is a clone of the arcade game where you move a craft, left or right at the bottom of the screen blasting a formation of aliens above. The aliens above move left and right, dropping bombs slowly descending the screen. In between yourself and the aliens are four shields, which lose parts every time you or the aliens hit one. If you are hit by an alien's bomb or an alien lands on the surface, then you lose one of three lives.

An early game by Jeff Minter of Llamasoft fame.