AstroBlast is a plain space shoot'em'up, a clone of the arcade game Astro Fighter, which evolved only slightly from the original Space Invaders. Just like in that game, your spaceship must shoot down slowly advancing rows of aliens, and with only one shot on screen at a time. The movement patterns are not yet evolved into something like Galaxian, since the enemies will never swoop down at you, instead moving in formation, but still slightly more advanced than Space Invaders, since they make small lopping patterns to make targeting more difficult. Of course, the barriers of Space Invaders are done away with, since this takes place in space.

Your spaceship has only one life, but three bars on its shield, which yields much the same result as three lives. What sets AstroBlast apart is the small amount of fuel that your ship has, and which can only be refilled every fourth level. You must therefore shoot down all aliens as quickly as possible, or you will run out of fuel before you reach the refueling level.