Darkside is a single screen top view shooter where you control a spacecraft on the left of the screen, moving up or down, blasting aliens from an invasion force that appear on the right of the screen. The aliens appear in various waves with three attacks by the same aliens in each wave, changing colour each time you destroy a set of aliens. As you blast, the aliens move to the left of the screen firing back at you with some bullets moving towards you and if you hit an alien or its bullets then you lose one of three lives. You can move forwards a short distance but you are pulled back to the left of the screen.