Logic Masters Deutschland e.V.

Digits surrounding a circle must sum to the number in the circle. Digits may not repeat around a circle.

Empty circles all represent the same sum, which the solver must find.

Numbers in the margin indicates the sum of digits between the 1 and the 9 in the corresponding row or column.

Normal Sudoku rules apply.

Try it at F-Puzzles or CTC app.

For an introduction to the rule-set, see this video of a solve of a similar puzzle.

Here is a slightly easier puzzle with the same rule-set: Overlapping Cages.