Galaxy on Fire is a 3D space combat and exploration game that was a lot of fun at its release in early 2009, but has since been eclipsed by other games in performance--especially its super-polished (and super-fun) sequel, Galaxy on Fire 2, which delivers exponentially on the promise of this original game.
The core of Galaxy on Fire 3D is space combat, and the game excels at providing an immersive, responsive aerial shooter (almost as good as its sequel), in which you can use touch or tilt controls to weave through pitched outer-space dogfights. The game also has some light RPG elements: you progress through a series of pre-set missions in the role of a Han Solo-esque mercenary with an Aussie accent, after which the galaxy opens up into a sandbox of systems that you can explore as you fight enemies, take on freelance missions, sell cargo, and upgrade your weaponry with the money you earn.
Unfortunately, it's this RPG aspect of Galaxy on Fire that quickly grows thin, with its very repetitive missions and only sketchily detailed universe. Fortunately, Galaxy on Fire 2 offers a much richer story, trading component, and more. Galaxy on Fire can be fun if you find it for free (or cheap) and you're just looking for a lightweight space shoot-'em-up--but hold out for Galaxy on Fire 2 if you want the complete package.