Logic Masters Deutschland e.V.

• Normal sudoku rules apply.
• Tentropy Mirror: Each cell has a digit in the same set of [19], [28], [37], [46], [5] as the cell reflected along the marked diagonal (e.g. if r2c6 is in the [28] class, r6c2 is also in the [28] class).
• Spaces outside the grid are skyscraper clues: they indicate the number of digits seen in that direction, for that effect, digits block any lower digit from being seen. Different letters represent different digits from 1-9. Filling the outer spaces is not required for a solution check.

Online in Sudokupad.

See also:

• a bonus box
• the perimeter of wisdom
• at the vortex spot
• diploptic triptych
• el quinto sol