Zero Tolerance is a first-person shooter developed by Technopop and released by Accolade for the Sega Genesis sometime in 1994. Zero Tolerance is the first and only first-person shooter sold worldwide for the Sega Genesis (its sequel, Beyond Zero Tolerance, was unreleased, while the Genesis version of Duke Nukem 3D was only distributed in Brazil).
The game uses a pseudo-3D, sprite-scaling, ray casting engine running on stock Genesis hardware. It was also one of the first FPS games to feature a female protagonist, Captain S. Ishii, along with Cyber Cop.
Planet Defense Corps. is an interstellar military conglomerate responsible for protection of space ships, colonies and space stations. Player controls the elite 5-man squad named "Zero Tolerance" which is sent on a mission to a space station Europe-1 attacked by alien forces.
After successful operation squad is informed that aforementioned attack was a decoy and the Planet Defense Crops. headquarters in a 165 story high-rise building, now invaded by aliens, were the true target. The only way to access the building is through the roof, protected by.
Squad has to descend several floors, fighting the aliens, who then fall back into under-basement levels of the building (which turn out to be the real source of the alien attack). Having enemy cornered, squad has to descend about twelve levels under the building, clearing the lair and killing the alien commander responsible for the attack.