TomZ Constrained Cube 90

As the name suggests, each face is constrained to turn by a quarter turn. Constrained Cubes Ultimate and 180 had enough freedom of movement to allow the use of normal algorithms, albeit adapted to contend with the puzzles' turning limitations. This is no longer the case with Constrained Cube 90. Losing the option to execute a Sune algorithm removes many solving options from rotating corners to permuting edges.

 

Solution

Step 1: Solve the White Edges

Intuitive

I have not figured out if this is the optimum way of solving the puzzle but I solve the white cross in such a way that one edge can be turned in the opposite direction from the other three. For example, one turns clockwise, the others anti-clockwise. This gives me one corner where I can execute a sledgehammer algorithm.

White becomes the bottom face.

Step 2: Solve the E-Layer Edges

Intuitive.

This is extremely fiddly. Moving edges around the puzzle is not easy with turning options so constrained.

Step 3: Orientate the Yellow Edges

I try to do this at the same time as step 2 but it does not always work out.

Step 3: Permute the Yellow Edges

This is a challenging step that requires some thought.

Step 4: Permute the Corners

This is fiddly but not as difficult as as it looks.

Step 5: Orientate the Corners

This step is not that difficult, especially compared with the steps.

This is a very challenging puzzle and, hence, all the more satisfying to solve. It is least an order of magnitude more difficult to solve than its brothers, Constrained Cubes Ultimate and 180. I would advise becoming familiar with at least one of those before tackling this puzzle.