The object of Boong-Ga Boong-Ga is to score points by spanking or performing kancho on a model of a human posterior embedded in the game's cabinet. A plastic finger is attached to the machine for players to perform the latter.
The game features eight characters players can punish: "Ex-Girlfriend", "Ex-Boyfriend", "Gangster", "Mother in Law", "Gold-digger", "Prostitute", "Child molester" and "Con-artist". During gameplay, the facial expression of the chosen character is displayed on a monitor.
The game also dispenses cards that rates players on their "sexual behavior", and for players who perform exceptionally well the machine will dispense a small plastic trophy in the shape of a pile of feces.
I don't know what's worse, the fact that this exists or the fact that they enjoy sticking their fingers up people's asses enough to make up a name for the technique.