Soviet Tag

Soviet tag (15 game, tag) - a popular puzzle.

It is a set of identical square tiles with numbers enclosed in a square box. The length of the side of the box is four times the length of the side of the knuckles for a set of 15 elements, respectively, one square field remains unfilled in the box.

The aim of the game — moving the knuckles on the box, to achieve ordering them by numbers, it is desirable to make as little movement.

It has a field size from 2x2 to 9x9.