Logic Masters Deutschland e.V.

Rules

The digit 1 must appear exactly once in every row and column. One is not part of either side or any region.

Divide remaining cells into two groups, the light side and the dark side, such that all light cells are connected and all dark cells are connected. No 2x2 block may be fully light or dark.

The digits 2-9 must appear exactly once in each row, column, and region. A region is an orthogonally connected group of cells that must be determined by the solver. Each region is entirely light or dark.

A digit in a circle belongs to light side and indicates the number of light cells in the line of sight of the digit including itself. A digit in a square belongs to dark side and indicates the number of dark cells in the line of sight of the digit including itself. Not all circles or squares are necessary given.

Numbers outside the grid are sandwich clues, which tell the sum of digits in light cells between 1 and 9 in the corresponding row or column.

Play this puzzle on CtC

Play this puzzle on F-Puzzles

5x5 Example

Example with smaller grid size. Sandwich clues show the sum of light cells between 1 and 5.