Logic Masters Deutschland e.V.

Mathgeek and I set this puzzle together as part of a setting competition, and we're very pleased with how it turned out. The rules are long, but hopefully they are intuitive, if you've ever solved a puzzle with quadruples or difference dots. Fun fact, the idea to place parity sweepers on edges and corners came to me as a result of a mis-click when trying to place one in a cell!

Rules

Normal sudoku rules apply: place the digits one to nine in every row, column and region without repeats.
All circles are parity sweepers, whose value is the count of odd or even digits in the surrounding area.
- A circle in a cell counts parity in that cell and the (up to eight) surrounding cells. The value in the cell must be the circle value.
- A circle on an edge between two cells counts parity in the (up to six) cells surrounding that edge. The two values in the cells touching the circle must differ by the circle value.
- A circle on a corner between four cells counts parity in those cells. The circle value must appear at least once in those cells.

Solve on SudokuPad.