Restricted Soma

Name
Restricted Soma

Designer
Martin Watson. This is the guy who designed the famous Digigrams puzzle.

Manufacturer & Availability
Manufactured by Brian Young of Mr Puzzle Australia. Available for AU$45/-

Type & Classification
3D Packing/Interlocking solid

Dimensions
Pretty heavy puzzle measuring about 7cm x 7cm x 7cm.

Materials & Construction
Looks to be Queensland Silver Ash for the pieces. The box is lacquered black. Construction fit and finish is very good.

Overview
This puzzle was Brian Young's IPP35 Exchange Puzzle.

To know what's a Restricted Soma, you need to know first what is a Soma. This Soma is "restricted" because the goal is remove the pieces and to pack them back into the box through a T-shaped opening....which of course makes it harder than the traditional Soma.

The puzzle came packed so the first task on hand was to remove the pieces. Not difficult and soon I had all out. With 7 pieces comprising of "simple shapes", it was not too difficult to remember where each piece went and I actually managed to get all the pieces back to their original positions inside. To aid in the solve, the box has round holes on all sides and the bottom, so fingers can go in to move the pieces about. But (unfortunately) the pieces cannot enter or exit from these holes!

The writing on one of the pieces states that there is more than one solution with rotational moves but only one solution that does not require rotations. I tried searching for this solution for a good part of the evening but not surprisingly, with no success. 

According to Brian on his site-

To find the unique solution without rotational moves is very difficult.  In a recent email even the designer admitted to having some difficulties although to be fair Martin did design it some time back so maybe it’s been a while since he tried to solve.

I don't feel so bad now. Burr Tools showed 3 possible solutions, but with one of the pieces doubling as a cover for the box, there is thus only one solution. And this solution involves some rather unusual moves. A total of 21 moves is required, with the 4th piece alone needing 8. A lot of fingering through the holes!

Difficulty
Not too difficult just to unpack and re-pack, unless you forget where the pieces are supposed to go. But as mentioned, very difficult to find the unique solution without rotation. It is rated as 7/10 by Mr Puzzle.

Summary

A must have for packing puzzle lovers.