Alien Assault is a delightfully retro space-shooter, reminiscent of older space shooters such as R-Type and Gradius.
You take the role of a pilot returning from a scouting mission who stumbles upon an alien fleet. You obviously have no choice other than charging in guns-a-blazing. You will fight many interesting bosses and a plethora of different enemies, all while collecting weapon and shield upgrades to increase your likelihood of survival.
The game only has one real song (excluding the two boss battle tunes), which isn't bad. However, it does get repetitive after the third (or so) time through. The graphics, however, look beautiful for being such small sprites. They all look amazingly detailed, and as much detail went into the planets that scroll by in the background as the evil bosses.
Alien Assault is a great way to spend an afternoon or a sleepless night.