Logic Masters Deutschland e.V.

Normal sudoku rules apply: place the numbers 1-9 into the grid so they appear in each row, column and 3x3 box exactly once.

Each cell in the grid should be colored either green or blue. Green cells represent land, blue cells represent water.

When a cell contains an arrow, the value of the cell shows how many cells share the same color with the cell in the given direction. E.g. when a cell is colored green, has an arrow pointing to the right and it's value is 3, there must be exactly 3 green cells in the given row right to (and not counting) the pivot cell. Not every possible arrow is given and the same-color cells are not necessarily next to each other or connected to the pivot cell.

An island is an orthogonally connected region of at least 3 land cells. Every land cell in the grid is part of an island. (Therefore single, separated green cells or two-cell islands are not allowed.)
Islands in the puzzle are separated by rivers, which are formed by a one cell wide stream of water cells.
Rivers form a single, orthogonally connected region in the grid.
2x2 regions of water cells would form a lake, which is not allowed in this puzzle.
Islands may touch diagonally, but they behave like Killer Sudoku cages, meaning land cells forming an island must have different values.




The puzzle is also available online at the following link: click here to try the puzzle
The link will take you to a great online pencil puzzle editor where you can solve the puzzle. You can use 'Surface' mode to add in the colors and 'Number' mode to write in digits (click 'small' or '1/4' to add pencil marks).


Have fun, and let me know what you think about this variant!


The ruleset of this puzzle is loosely based on the great pencil puzzle Nurikabe by Nikoli.