# Interlocking 20-Ball Tetrahedron

The Interlocking 20-Ball Tetrahedron is a new polysphere puzzle by George Bell. You can purchase a copy from Poly Puzzles. This puzzle is closely related to one called Blossom, invented in 1995 by Bernhard Weizorke. The major difference is that my puzzle cannot be assembled if the pieces are rigid, and cannot be assembled in the same way as Blossom. The pieces must be slightly flexible, and for this reason it is difficult to make it out of wood. Plastic that is flexible, yet strong, works well.

## Solution Hints

Observe the four puzzle pieces carefully.

Note that the four pieces are not identical. Instead there are two identical pieces and two identical mirror images (left and right pairs above). One end of each piece ends in a 90 degree angle connection between two balls (bottom of each piece in the above photo), while the other ends at an obtuse angle (top, 120 degrees to be exact). The pieces are also not planar, which adds to the confusion.

Here are some easy hints to get you started assembling the puzzle

1. Begin with two identical pieces. In what follows, we will use the two right-hand pieces in the above photo, but either will do.
2. The balls at the ends of the obtuse angles end up at the corners of the tetrahedron.
With these hints, you may now want to try to solve the puzzle on your own. Please do not look at the solution page until you have really spent some time with it.