Logic Masters Deutschland e.V.

Inspired by IcyFruit's Taiga, with (in my opinion) a mad but very interesting indexing rule.

• Sudoku: Each row, column, and region indicated by thick borders in the grid must contain the digits 1 to 9 once each.
• Indexer cells: Identify two "indexer" cells in each row, column, and box, with one indexing in the row and the other indexing in the column. The digit in an indexer cell indicates the position of the other indexer cell in its row or column. Positions are counted left to right in rows and top to bottom in columns. See below for an example.
• Killer cages: An area surrounded by a dashed line is a killer cage. Digits in a cage sum to the number in the upper left corner if given. Indexer cells cannot appear inside a killer cage.

You can play this puzzle online using Sudokupad: https://sudokupad.app/fz5pm5733u, or Penpa+: https://tinyurl.com/b3jh7t7k.

Example:

To clarify the indexer cell rule, below is an example of a 6x6 sudoku with the same ruleset. In the solved grid, cells indexing in their column are marked orange, and cells indexing in their row are marked blue.

You can play this example puzzle on Sudokupad: https://sudokupad.app/6ftoxo6mf1, or Penpa+: https://tinyurl.com/5cbtza7h.

In the image of the same solved grid below, arrows mark which cells are indexed by each indexer cell. Note that in general it is not necessary that there is only a single chain of indexer cells forming a loop.