risTroyka is simple, but very addictive puzzle game played on a 10x18 playfield. From the top to the bottom of the playfield are falling down columns composed of three blocks, which colours are randomly choosen from four basic colours (red, green, blue and yellow), but in one column there can only be two blocks with the same colour. Each column stops falling, when it either hits the bottom of the playfield or hits remaining block. When column is placed on playfield, each row from bottom to top and left to right and each column from left to right and bottom to top is checked if there is Troyka - three blocks with the same colour. Collected blocks are deleted, so all blocks above fall down and replace them. If there is no vertical or horizontal Troyka, new column starts to falling down.