On the playing field is a stone door, consisting of 16 blocks. On blocks are located colored crystals and rings. Number of crystals of each color is always equal to the number of rings of the same color. You must place the crystals so that they coincide with the color of the color ring.To move the crystals click the screen in the center portion of the four blocks. In this case, four crystals located on these blocks will immediately move clockwise to the next position. Keep doing this as long as all the 16 colored crystals will be in the rings with the same color. Think carefully about each move.