A
mechanical puzzle that appeared during the big
fad of
Rubik's Cube-like puzzles in the early
1980s. This one consists of a
tetrahedron with its faces each split into 9 small
triangles.
This puzzle is much easier to solve than the Rubik's Cube because its construction provides far fewer arrangements of the thing. Each corner pyramid spins freely on top of the piece to which it is attached, which contains all three of the mini-triangles adjacent to the corner (on three different faces) -- in effect, those pieces are the real corner pieces and the actual corners are just so much decoration. Effectively, then, six of the nine small triangles on each face are all corner pieces, and the arrangement of colors on the faces is determined by these pieces. Solve these first, and then the remaining pieces, six edge pieces, are solved without too much further difficulty.
The nrt rides again!