Crystal structure "white tin" respectively. Two more allotropes, γ and σ, exist at temperatures above 161 °C and pressures above several GPa. White tin is metallic, and is the stable crystalline form at or above room temperature. Below 13.2 °C, tin exists in the gray form, which has a diamond cubic crystal structure, similar to diamond, silicon or germanium. Gray tin has no metallic properties at all, is a dull gray powdery material, and has few uses, other than a few specialized semiconductor applications. Although the α–β transformation temperature of tin is nominally 13.2 °C, impurities (e.g. Al, Zn, etc.) lower the
Puyo Puyo! 15th Anniversary from the Madou series, who serve as boss characters in the story modes. As "Puyo Puyo! 15th Anniversary" was created to commemorate the fifteenth anniversary of Puyo Puyo, it includes most of the "Fever" characters plus six of the characters from the "Madou" series; they are said to have fallen from the sky into Primp Town, the primary setting of the Fever series games. There are a total of twenty-two characters in this game. 15th Anniversary has a slew of new modes, and also includes modes that emulate the original "Puyo Puyo", "Puyo Puyo Tsu" and "Puyo Pop Fever". In