Logic Masters Deutschland e.V.

Psycho Look-and-Say Killers are one of my favorite indexing constraints. They index digits across the grid in a unique way. This variation includes cages without given clues! Good luck and good logic with the puzzle!

The puzzle title is taken from the chorus of the song Psycho Killer by the Talking Heads.

There is also an introductory puzzle available for an easier introduction to the constraint: Intro to Psycho Look-and-Say Killers.

Rules:

• Normal Sudoku rules apply, along with Arrow and Psycho Look-and-Say Killers.
• Sudoku: Place the digits 1-9 once each in every row, column, and 3x3 box.
• Psycho Look-and-Say Killers: Digits in pink cages may not repeat. Each digit in a cage indexes a cell in the grid. The cell is located in the *box* with the digit's number, in the *same position* within the box as the cell containing the digit. A digit may index its own cell. The cage clue should be read as a look-and-say clue that counts the number of times a digit appears in all the indexed cells.
• Cage clues are two digit numbers which must be determined by the solver. Each ? in the clue must match a digit in the cage. Both ? may match the same digit.
• Each cage must have only *one* valid clue. Different cages may have the same clue.
• For example, a cage containing the digits 238 would have a clue containing only 2's, 3's, and 8's. If the clue was 28, then there would be exactly two 8's in the cells indexed by the digits in the cage.
• Ambiguous Kropki Pairs: Digits separated by a gray dot must either be consecutive or be in a 2:1 ratio. Not all dots are necessarily given.

Streamers have permission to use this puzzle.

Play in SudokuPad

Example:

• In the example image, there must be two 8’s in the cells indexed by the 28 cage in box 2.
• The digit 1 in that cage indexes to *box* 1, and then to the cell in the *same position* in that box as the digit 1 in its box (the top-middle cell).
• The digit 3 in that cage indexes to *box* 3, and then to the cell in the *same position* in that box as the digit 3 in its box (the middle-middle cell).
• Since there must be two 8’s in the indexed cells, both indexed cells must contain an 8.