This is a remake of the arcade game Steel Gunner which has had the graphics heavily pixelated. They've also changed the main character into a girl, but I didn't see any adult content. Maybe I'm just terrible at this game, but I couldn't get past the first level. Left mouse is standard shot, right mouse is your missile.
HardcoreGaming101 was a lot better at playing this game, and has some discussion of it and how it falls into the whole Steel Gunner series, such as it is.