the threepeater is a plant in this game, which shoots in three lanes. the lane above, the lane its on, and the lane below, right? the threepeater has three heads, each one layered vertically in order to make them visible to the player. whenever a zombie is within one of the three lanes, it fires, and each of it's heads bob in order to show the action and give it a bit more life, as all the plants do. however, if you place the threepeater at the top or bottom lanes - lanes which it cant possible shoot all three - the top or bottom heads respectively wont bob when the threepeater fires, as it's not firing in those non-existant lanes, while the others still will. this game is 5 bucks on steam in case youre wondering