Tank 1990 is a modified version of Battle City created by the Chinese bootleg developer Yanshan Software. This hack features 15 alterations of the original game, each marked from A to N. Each hack introduces unique level combinations with varying enemy tank formations. Enemy tanks display unusual traits, such as small tanks having armor similar to large ones, or large tanks appearing without armor. New power-ups are also introduced, including a gun icon that instantly upgrades the player's tank and a ship icon that allows water movement. Watch out—enemy tanks can also collect these power-ups!