Logic Masters Deutschland e.V.

This is the second puzzle of this variant. The ruleset is the same as before, but this one should be considerably harder, so if you have not solved the previous one, I'd recommend starting there. :-)


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.





Have fun!


The arrows are placed in the center now, not on the edges, but their meaning is the same as before. This layout change was needed so it's easier to spot the symmetry of some arrows, which might prove to be very important in many cases.

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