 In the "kill them all" levels, which are mostly every 10 levels or so, there are no EZT crystals and the player's goal is to destroy all the Clagnor "drones" in the level.In the bonus levels, which are usually every 5 or 10 levels, there are neither Clagnor nor EZT in the area, and so the player can freely travel around and collect weapons, ammunition, and shield bonuses for a limited time.Because the level's goal is chosen at random, it means the player can potentially get 3 bonus levels "in a row".