Logic Masters Deutschland e.V.

Quattroquadri: Normal Quattroquadri rules apply. Put the digits 1 to 9 into each box such that no digits repeat in any row or column.
Loop: Draw a single, non-branching, non-intersecting loop in the grid that travels along the cell borders. If two orthogonally adjacent digits are both inside the loop then their sum is less than 10. If two orthogonally adjacent digits are both outside the loop then their sum is greater than 10.
Arrows: A digit in a cell containing one or more arrows counts the total number of loop segments pointed to in the indicated direction(s).
X: Digits on an X sum to 10. Not all Xs are given.

Links:
SudokuPad: https://sudokupad.app/0n55pabvxs