Logic Masters Deutschland e.V.

Play the puzzle online here!

Rules:

• Normal sudoku rules still apply.
• Color each square as either 'land' or 'water'
• Each contiguous orthogonally connected set of land cells forms an 'island'
• Similarly, each contiguous orthogonally connected set of water tiles forms a 'lake'
• The largest digit in each island is equal to the total number of cells in that island
• The smallest digit in each lake is equal to the total number of cells in that lake
• The leftmost cell of the uppermost row of each island or lake may contain a number corresponding to the sum of the digits in that island or lake. Note that not all lakes or islands necessarily have their sum displayed. The question mark indicates that that square is the top leftmost square of an island or lake, but no sum is given.
• A circled cell indicates that its digit is equal to the total number of land squares in its 2x4 region.