Cosmic Guerilla is a bit of a horizontal variation on Space Invaders. Without the artwork, it just looks like your gun is shooting aliens stealing your rectangles. But the artwork shows you're a dinosaur-riding Aztec warrior defending beautiful women from horned alien demons.
There were at least two versions of the header. This is a recreation based on the German version, just because it's the only one I could find a decent photo of. The US/Japan version has psychedelic swirls on both top and bottom.