Infection is a platform/shooter. You move through stages killing off the life infected by a strange mist let off by an asteroid. It has allitle bit of a metroid style but is much more linear. There isn't really any exploration to do at all. You will pass through 5 levels full of death and monsters. Overall there is about 40 rooms with 2 save points farther in the game so you have to be pretty good to beat it.
