Logic Masters Deutschland e.V.

Puzzle link: Play on CTC SudokuPad.

Rules: Normal Sudoku rules apply, i.e., place the numbers 1 to 9 once each into each row, column, and 3×3 box. A number in a cage indicates the sum over all digits that are orthogonally or diagonally adjacent to that cage but outside of it. Sums in two-cell cages are written in ordinary left-to-right notation with the tens digit in the left cell and the ones digit in the right cell. Grey cells contain square numbers.