Logic Masters Deutschland e.V.

Inspired by Stacked Sandwiches Sudoku.

Rules:

• Normal sudoku rules apply, i.e. each of the digits from 1 to 9 needs to appear exactly once in each row, column, and 3-by-3 box.

• Arrows of the same color (white or black) pointing at each other in the same column or row indicate a 'sandwich'. The arrow cells are the boundaries of the sandwich and they must contain the sum of all the digits enclosed between the boundaries. Such a sum must have two digits, and each arrow cell contains one of those digits. For instance, the white arrows pointing at each other in row 2 enclose 3 cells. Examples of valid options for the 5 cells (-> arrow cell, enclosed 3 cells, <- arrow cell) are 1 3 4 5 2 because 3 + 4 + 5 = 12, or also 2 5 3 4 1 because the order does not matter, or 1 7 5 9 2 because 7 + 5 + 9 = 21. Remember though that the 1 and 2 of the 12 or 21 total in this example must always go into the cells containing the white arrows.

You can play this puzzle online using Penpa.

If you wonder what the given 6 does in a lunch box, I imagine it to be a little coffee cup.

Good luck!

Edit: I'm worried that the puzzle may be too hard if one of its core pieces of logic is missed, so below is a hint if you need one. Spoiler alert, obviously.

There's something odd about the three sandwiches in boxes 4 and 5.