Your aim is to hold off the enemy as long as possible, and delay what seems to be an imminent defeat. This game has 26 different enemy types and 6 different kinds of weaponry. A Victory game finishes after level 40 and you will receive your score. A Defeat game has no end and you are scored on how long you survive. At the end of each level, you can repair your armor and purchase more armor and weapons and gadgets with the money your make. A boss will appear at the start of every fifth level up to level 20. This boss will consist of a wave of units appearing all at once. Normal attacks may resume before the defeat of the boss so be quick.