Metal Gear Acid 2 (stylized as Metal Gear Ac!d ²) is a turn-based collectible card stealth game developed and published by Konami for the PlayStation Portable in 2005. A Java ME version for mobile phones was released by Glu Mobile in 2008 titled Metal Gear Acid 2 Mobile. Acid 2 is the sequel to the original Metal Gear Acid, with the story set sometime after the events of the previous game. Like its predecessor, it follows an alternate continuity separate from the mainline Metal Gear series. The game uses a completely new cel-shaded graphic engine, replacing the darker graphics from the first game, and features an improved gameplay system. It comes with a PSP add-on called the Solid Eye, which is a folding cardboard box with specialized lenses that fit over the PSP's screen, creating a stereoscopic image.