In X the player pilots a space tank sent to another planet to defend the earth from an alien invasion. There are ten missions with different objective ranging from restoring power to a power plant, to 'seek and destroy' missions. The player can guide the tank freely across the over world, but there are enemy patrols that will open fire. The alternative is going though underground tunnels, where there are spots to replenish the tank and its weapons. The player only has a limited amount of time for each mission, and shielding for the tank. If either runs out, the game is over.