BrainCube
BrainCube is a unique 3 dimensional letter puzzle similar to Sudoku. BrainCube is played in a cube of 64 squares using the letters A-P. The cube has a stack of four boards with 16 squares on each board.
The object of the game is to fill in the missing letters so that each board has one of each letter A-P and each 16-square "slice" of the cube from front to back and right to left also have one each of the letters A-P.