The 13 is a logic-based puzzle for Android. Unique mathematical concept explores the sacred geometry of number 13 and turns the player into an alchemist. Sequences of 12 golden plates appear on the 13-square alchemist Matrix filled with 12 lead bars and 1 catalyst gold bar. Each plate contains a philosopher’s stone in one of its 5 blocks. The objective of the game is to turn all lead into gold by positioning philosopher’s stones over the lead bars while keeping the plates inside the Matrix. However, if the bar under the stone is already gold, the whole Matrix turns into lead again! Plates can be rotated and moved over the Matrix 13 times by sweeping and tapping on the screen. A double-tap completes the move and the game ends after 13 minutes. With every Matrix completely filled with gold the game enters a new level. As the game progresses, it becomes more random and difficult. It challenges the brain in 13 increasingly difficult levels. The game combines fast paced action with deep thinking and guarantees hours of entertainment.