Metal Gear Acid 2, is a turn-based collectible card stealth game developed by Kojima Productions 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. Gameplay Gameplay in Metal Gear Acid 2 is similar to that of its predecessor, using a series of collectible trading cards based on the other Metal Gear games. There are new features, such as the SELL option for cards, allowing overstocked cards that the player cannot use to be sold for more points (in-game currency used to buy cards) and cover fire (when a player's ally is behind an enemy and has an equipped weapon in range of the target, when the player attacks, the ally takes a shot onto the target as well). Also added is the ability to move past doors instead of stopping when approaching, and characters can now pick up items such as weapons and card packs by simply running over them (instead of having to end movement on top of the item). The game uses a revamped engine, featuring a cel-shaded presentation, 3D equipment boxes, and new particle effects. There is a tutorial mode for beginners and a new "Arena" single-player mode that allows players to battle boss characters from previous games, such as Liquid Snake and Vamp, using the Acid 2 card-battling system. There are also extra missions such as "Sneaking" and "Elimination" modes. The game can be also played in the "Wireless Battle" mode (using ad hoc connection only). An additional "Solid Eye Theater" mode allows users to watch videos of the Japanese women seen on posters and magazines throughout the Metal Gear series, utilizing the Solid Eye attachment. Card system The gameplay system consists primarily of the usage of cards (obtainable in-game, through a card shop, or