this puzzle is equivalent to a Redi Cube, but in the shape of a tetrahedron instead. because of this, what appear to be centers on the tetrahedron turn like corners as well. to access the last four corners, you need to turn each of the "tips" by 120º. when everything is aligned, the puzzle turns great; unfortunately, however, there is no alignment mechanism, and it's very easy to to turn the other corners just slightly beyond the 120º angle, thus blocking the turn. this puzzle is close to being a super playable fun, but it gets frustrating to solve with its current design.