Battle City (known as Tank in some regions) is a multi-directional shooter video game. It is a port of the arcade game Tank Battalion with additional features (including two player simultaneous play, and an edit feature, both explained later).
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 or Phoenix), 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.
Source: Wikipedia, "Battle City (video game)", available under the CC-BY-SA License.