Gunbound is basically an online tactical mobile game. You pick a mobile and some items that are usable in-game before you start off a game against opponents (up to 4x4, odds always start off the same). Once inside a game, you move around your mobile, adjust your angle and use your power bar to shoot with your mobile, aiming to either cause damage to an opponent or making him fall off the map (which happens once all of the ground he's in is destroyed). The objectives of a game itself tend to depend of the mode of the game. For instance, in one of them, you only need to kill off your enemies, while in another one, you have to accumulate a certain amount of points (originated from "jewels' that you must hit) in order to win.
tl;dr, Gunbound = Get a mobile and shoot enemies. It's quite fun. Go to
http://gunbound.ijji.com/ if you happen to be North American, or go to the international one here:
http://www.softnyx.net/