An aging platformer that adds a flamethrower but not much else to the genre.
Graphics: The art is kind of fun and doesn't take itself too seriously. However, the sprites get very repetitive and the level tilesets are reused endlessly. The weapons and explosions make it all worth it, though.
Sound: The sound is bad. I mean really bad. This game was released around the time of Doom and X-Wing, and it should have been better with some real voice sampling. The music is nothing to write home about, and the weapons sound anemic. Turn off the sound and play some MP3s in the background.
Gameplay: You move through maze-like 2D levels of office buildings or sewers to rescue citizens that have been captured by zombies/aliens/evil thingies. Think of Super Mario Brothers except you fly with a backpack instead of a raccoon tail or cape. The jet pack is powered by the same fuel used in your flamethrower, so you need to keep an eye on fuel and ammo throughout the game. You can always buy more, though, at vending machines throughout the levels. The best part of the game is the secrets. When this was developed, it was very popular to have false walls and ceilings you could travel through to get to reward areas. Finding them always feels like you discovered something special.
But this isn't a special game. It's standard fare, and if you're considering it I'd heartily point you towards the Commander Keen series (episodes 4 and 5) for a far superior 2D platformer that exudes just as much nostalgia.