Not a great game, but near and dear to me
The game is a typical overhead shooter a la Xevious, where you get power-ups (in the form of letters you fly over to pick up) to upgrade your ship and with enough Energy stored up (by running over big red E's, but watch out, backward E's make you lose energy!), you can change your ship to a different form that possess a special attack or ability -- such as a flame turret or shield.
It starts off innocent enough with a few enemies trying to take you down, but quickly the difficulty increases. One hit and you're dead, unless you get the shield ability. It can get tough, but not impossible. At the end of each mission is a weird alien-ship boss, that you have to kill, obviously. Each level's looks unique, but usually consists of a similar attacking pattern - swerve around the screen in a wave-like motion, all while tossing out lots of bullets to try and take you down.
There is really nothing memorable about the game, but for some reason the whole power-up system hooked me in some odd way. I still go back from time to time and play it, only to give up in frustration before completing the second mission. I somehow beat it when I was 7, but can't seem to repeat that accomplishment. Perhaps it's because it was one of the first games I bought with my very own allowance money, so I felt obligated to finish it.
All in all it's a pretty generic shooter, with a somewhat unique upgrade system, okay graphics and sound, and interesting bosses. Might be worth looking at if you were the type of kid that liked to make words out of alphabet soup? Maybe?