Spots from MyDevCorp

Spots is a popular puzzle game invented in 1878 by Noah Chapman. It is a set of identical square knuckles with printed numbers, enclosed in a square box. The length of the box is four times the length of the side of the 15-element set of knuckles, respectively, the box leaves one square field unfilled. The goal of the game is to move the knuckles through the box to achieve ordering by numbers, preferably by making as few moves as possible. The application has 4 levels of difficulty, from three to six rows of dice.