Cube (algebra) however, easy to show that most numbers are not perfect cubes because "all" perfect cubes must have digital root 1, 8 or 9. That is their values modulo 9 may be only −1, 1 and 0. Moreover, the digital root of any number's cube can be determined by the remainder the number gives when divided by 3: Every positive integer can be written as the sum of nine (or fewer) positive cubes. This upper limit of nine cubes cannot be reduced because, for example, 23 cannot be written as the sum of fewer than nine positive cubes: The equation has
Curiosity: What's Inside the Cube? messages. Players tapped the cubelets to dig through the surface of each layer and reveal the next layer below. The goal was to reach the center and to discover what was inside the cube. Each layer, which had a distinct look or design, contained a clue as to what was in the centre of the cube. Each cubelet destroyed by a player awarded them coins. Coins could be spent on tools that temporarily enhanced the player's abilities, such as picks ranging from iron to steel to diamond that increased the number of cubelets destroyed with each tap, or firecrackers that