Metal Gear Ac!d 2 released in 2005 exclusively to Playstation Portable. The ACID acronym stands for Active Command Intelligence Duel. Directed by Shinta Nojiri, Ac!d 2 continues the turn-based card gameplay from the first Ac!d game. The story is unrelated to the rest of the series. Ac!d 2 features new cel-shaded graphics and a cardboard box add on.