Objects can be destroyed by running into an explosion, allowing for clusters of enemies to be destroyed with a single hit. Unfortunately, this also applies to the player's base, making it possible to be killed by a low-altitude target that has just been destroyed. The sky changes color when the player reaches certain point levels: Black (starting); Blue (1,000-4,999); Purple (5,000-19,999); Turquoise (20,000-49,999); Gray (50,000-99,999); Black (100,000+). A multiplier is applied to all point values, starting at 1 and increasing with each new level to a maximum of 6.