In November 1990, an add-on campaign, named "Wing Commander: The Secret Missions", was released, adding new missions, new ships, a new storyline, and an increase in difficulty. Unlike the original game, "The Secret Missions" does not feature a branching mission tree; every player plays the same missions in the same order. However, if the player does not fulfill the mission requirements at any system, he immediately plays the two losing "retreat" missions that are not on the winning path. "The Secret Missions" was also released for the SNES as a stand-alone cartridge.