Hyperspace Invaders Zero is a collection of (3) explosive arcade shooting games.
The main mode, Soulgrinder, is an all-new vertical scrolling shmup (shootemup) featuring 100+ traininglevels, huge swarms of invaders, impossible bossfights, bullet chaos, adaptive difficulty and a nerve-wrecking soundtrack + bonus Atomhead MP3 EP.
If you play well enough, you also get to unlock 2 retro remakes, based on oldskool classics such as Space Invaders (1978) *including a 2P mode* and Paratrooper (1984).

Read all about it on the official website: HI0 at Entity Medialab