The game is set in the year 2117, two years after a cataclysmic Antimatter War. The player leads a military force whose main unit is the Metal Marine: a 16-meter (50 ft) high, 93-plus ton mecha. The game feature a number of minor gameplay differences, namely the plot. In the PC version the player controls a commander of the “United Earth Empire” (“Empire” in short) a futuristic version of United Nations. The adversarial Zorguef’s force is a dictatorial government.
After conquering all space colonies, Zorguef sets his eyes on Earth and the player must take up arms to protect the planet. In the SNES version the player controls a commander of the “Space Colonies Allied Forces” (“SCAF” in short), an alliance formed by the independent space colonies. The primary mission is to take the battle to the Earth, which is currently in the grip of Zorguef’s empire. The goal is to save the humans living on Earth who are being oppressed by Zorguef while securing the future of Space Colonies.
The game composes of 20 missions where the player will slowly regain the conquered territories of the Earth until the enemy force is defeated. The game is played in an isometrical style when building and in an aerial grid style when planning an attack to the enemy territory. Inside the game the player focuses on building both offensive and defensive structures to be able to attack the enemy territory and defend his own. Every structure except the I.C.B.M. silo occupies one square into the map.