Logic Masters Deutschland e.V.

Normal sudoku rules apply. In addition:

• Green Cells: If a cell in box N is green, then the digit in that cell is the number of boxes in the completed grid which have N in the same position as that green cell. For instance, if R1C1 is green and contains a 2, then there are exactly 2 boxes which have 1 in the upper left-hand corner (because R1C1 is in the upper left-hand corner of box 1). There is no negative constraint; not all possible green cells are necessarily given.
• Arrows: The digits along each arrow must sum to the digit in the circled cell. Digits may repeat along an arrow if permitted by other rules.

F-puzzles: https://f-puzzles.com/?id=yxzjjh7a

CTC: https://tinyurl.com/47m8ch2w

You can try a slightly easier puzzle which uses the same 'green cells' constraint here.