Tubeway

You are exploring the outer reaches of space, when beings from a strange geometric universe begin to break into your reality with the intent to invade Earth. The alien force shields have locked you into the outer rim of their geometric tubeways, where you must shoot down the enemy vessels before they can enter your dimension.

The player controls a target-shaped vehicle, which can skim the outer rim of varying geometric shapes The player fights against homer and seeker vessels, which are worth 100 and 200 points respectively. The player must shoot all incoming vessels to advance to the next stage, which will feature a new geometric shape and more oncoming alien vessels. Players are rewarded bonus points based upon the time they have remaining after finishing a stage. If a player runs out of time, the germ will break free from its confines in the lower left corner of the screen, and hunt down your vessel. The player starts with 3 vessels, but will gain an extra vessel for every 20,000 points they accumulate. Lose all of the vessels, and it's game over.