Logic Masters Deutschland e.V.

Rules:

-Normal sudoku rules apply.
-There are 9 cells, one in each row/column/box, which are doublers. For the purposes of the constraints, doublers double the value of a cell. Each digit from 1-9 is doubled exactly once.
-No adjacent pair of values along a purple line (not counting the bulb) may sum to greater than the value in the bulb.
-Values in a cage must sum to the number in the top left corner of the cage (or sum to a total that satisfies the given inequality). Digits cannot repeat in a cage, but values may.
-The value in the white circle indicates that value must appear in one of the four surrounding cells.

Links:

F-puzzles
CTC