Logic Masters Deutschland e.V.

This puzzle combines features of X-sums and sandwich sudokus.

First, standard Sudoku rules apply: Fill the grid with numbers from 1 to 9, so that every row, column, and 3x3 box contains each of the 9 numbers exactly once.

A number to the left of a row shows the sum of all numbers in the row between the X-th cell from the left end and the Y-th cell from the right end, where X is the number at the left end and Y is the number at the right end. Numbers above columns work similarly. Here are a few examples:

If the row has 246918753, then X=2 and Y=3. The X-th number from the left is 4 and the Y-th number from the right is 7, so the clue for the row would be 6+9+1+8 = 24.

If the row has 719283546, then X=7 and Y=6. The X-th number from the left is 5 and the Y-th number from the right is 2, so the clue would be 8+3 = 11.

If the row has 548973216, then X=5 and Y=6. The X-th number from the left is 7 and the Y-th number from the right is 9. There's nothing between 7 and 9, so the clue would be 0.

If the row has 492578316, then X=4 and Y=6. The X-th number from the left and the Y-th number from the right are both 5, so again the clue would be 0.

If there's no clue next to a row or column, then the sandwich sum can be anything.

I created this puzzle several months ago, but decided not to publish it then to avoid confusion with Big Tiger's battlefield sudoku puzzles. If you're familiar with those, note that the rule here is slightly different: In the 'overlap' case, the battlefield sum includes the end cells of the overlap, but the XY-sandwich sum does not.

The puzzle is available on Penpa.