Atlantis is a variation on the shooting game genre popular in the early 1980s. The player controls the last defenses of the city of Atlantis against the alien invaders. The city has seven bases, which are vulnerable to attack. Three of these have firepower capabilities to destroy the Gorgon ships before they manage to drop bombs on one of the settlements. The gun bases have fixed cannons; the center base fires straight up, while the far left and far right bases fire diagonally upwards across the screen. The enemy ships pass back and forth from left to right four times before they enter bombing range, giving an ample opportunity to blow them away. Lost bases can be regained by destroying enough Gorgon ships. However, regardless of the player's efforts to avert the tragedy, Atlantis is doomed. The only way the game can end is when all bases are destroyed. However, a tiny ship then rises from the rubble and speeds away, foreshadowing the events of the sequel Cosmic Ark.