The player, controlling a tank, must destroy enemy tanks in each level, which enter the playfield from the top of the screen. The enemy tanks attempt to destroy the player's base (represented on the map as a bird, eagle, orPhoenix), as well as the human tank itself. A level is completed when the player destroys all 20 enemy Tanks, but the game ends if the player's base is destroyed or the player loses all available lives. Battle City contains 35 different stages that are 13 units wide by 13 units high. Each map contains different types of terrain and obstacles. Examples include brick walls that can be destroyed by having either the player's Tank or an enemy Tank shoot at them, steel walls that can be destroyed by the player if he has collected three or more power-up stars, bushes that hide Tanks under them, ice fields that make it difficult to control Tank and pools of water which cannot be crossed by Tanks. There are four progressively harder types of enemy Tanks.