With its circles on each face, the Calvin's Void Tornado Wheel Cube (Black) is a puzzle that turns corners and adds another level of difficulty. This cube adds a strategic element to every step since, unlike ordinary twisty puzzles, it requires accurate circle alignment before some rotations become viable. This one has parts attached to the corners that are visible via holes in the middle. These internal bits will become scrambled if the puzzle is scrambled, making it harder to solve.