Made for the ludum dare 48 hour game compo, this is a game with solid game mechanics and very simplistic graphics (which is the opposite of what's usually happening there). Your character is a square that fires smaller squares. Your bullets can kill enemies (which is the game objective) on a level, but they can also puncture walls. What's the game's gimmick though is that whenever your (or the enemies') bullets hit something, some debris pixels appear. You can suck these to increase your bullet cache (as it decreases as you fire).
Give it a go, it's worth it I think.