Emeraldia (エメラルディア) is an arcade game that was released by Namco in 1993 only in Japan. The player must line up blocks of the same color. When three blocks have been stacked in a vertical row, they crack. When a fourth block of the same color lands on the cracked ones, all four blocks disappear. Source: Wikipedia, "Emeraldia", available under the CC-BY-SA License.