Hyperspace Invaders Zero
Hyperspace Invaders Zero is a frantic vertical shooter with abstract graphics where you blast away massive amounts of enemies and collect their souls to increase your firepower.
Gameplay itself is pretty minimal because only the left and right arrow keys are needed to control the ship and its slippy laserbeam. However the simplicity doesn’t make it an easy game due to the sheer amount of stuff that is happening on screen.
Moreover by reaching a decent score you will unlock a Space Invaders and a Paratrooper remake.
There is also a sequel available called Hyperspace Invaders I