This is a variant which I've been working on lately & The original Thread and my 1st 3 puzzles can be found here. The concept is quite close to some other variants like Orthogonal Sudoku, Graeco-Latin Soduku & Setdoku. Sudoku^2 is different enough to justify a name on it's own.

16 symbols for a regular 16x16 sudoku. Each symbol can be broken down into two different symbols. We end up with two groups of 4 symbols. Each group can form a regular 4x4 sudoku in each of the 16 boxes of the 16x16 sudoku!

I've tried these & were very addictive. I have managed to create the symbols in a way that would allow Black & White printing.

The original 3 puzzles will posted again here as puzzles 1-3.

Difficulty Ratings:

Very Easy : Combined Sub-Symbol Singles Only Needed

Mild: Sub-Symbol Singles Required

Moderate: Beyond Singles but nothing more than intersections and/or Hidden doubles

Severe: Beyond moderate but still can be solved with a pencil & paper (May require Naked doubles and/or Triples and/or X-wing)

Profound: At the moment this is left to describe puzzles beyond Severe difficulty.

I've posted a walkthrough for puzzle02 if you need an idea about how to solve this type of puzzle.

I also have been using a single character identifier for row/column/boxes instead of numbers, because It uses UTF-16 characters it doesn't display well on all formats. I have been using it to represent the 81 symbols Setdoku but the 1st 16 symbols are universal

Enjoy,

[Removed String As it had UTF-16 characters & Added Very Easy Rating]

Tarek