This is very much another version of the "Galaxians" game. The idea is to kill off the swarms of aliens which proceed down the screen at you. Every so often, the PAPER/INK colours change, making for some pretty weird combinations. After a while you are even lucky enough to get different shaped aliens.
Though Alien Swarm may be quite well written, it cannot compete with the other 'Galaxians/Invaders' clones such as Imagine's Arcadia, which I reviewed two issues back.
Overall, this game may be quite fun but rather predictable and not very innovative.