Fire Galaxy is a clone of Konami's Scramble, with pieces of its follow-up Super Cobra added.
The premise is the same as in the original: Fly into a side-scrolling cavern system and shoot everything that moves, while keeping an eye on your fuel level. Drop bombs on fuel silos to avoid crashing. Early enemies are rockets launching from the ground while shooting at you, followed by enemies hovering around in the air, missiles flying fast in your direction, aliens bouncing up and down in your path, a fleet of spaceships and swarms of aliens.
Another enemy is the landscape itself. Avoid crashing into the walls of the levels during evasive maneuvers. The landscape never really narrows down like in so many other scramble clones, but instead there are formations like stalactites and stalagmites, much like in Super Cobra. The aliens regenerate unless you pound them repeatedly.
Fire Galaxy uses a character based scroller, scrolling in 8-pixel increments, with big sprites on a large screen.