Logic Masters Deutschland e.V.

For an easier version, replace the >8 cage with an 11 cage.

Rules:

-Normal Sudoku Rules Apply.
-Shade some cells in the grid, in which those shaded cells are seen as negative numbers (e.g. if r1c1 was shaded and was a 1, then it means -1). Clues outside the grid give the total sum of all digits of the same polarity in the row/column.
-Digits in a cage (with their corresponding polarity) must sum to the number in the top left corner of the cage. Digits may only repeat if they are of different polarity. (e.g. a three-cell 7 cage may be 5, -5, 7 but not 2, 2, 3).

Links:

F-puzzles
CTC