Logic Masters Deutschland e.V.

After seeing Rangsk's solve of this puzzle, I think it may have been a bit too grindy, so I eliminated some steps using the dot in box 3 (though I suspect this may not be enough).
I should probably add: I probably only recommend solving it if you enjoy tough puzzles.

Rules:

-Normal sudoku rules apply.
-Digits on an arrow must sum to the number in the attached circle. Digits may repeat if allowed by other rules.
-Any set of 3 digits along an entropic (orange) line must contain exactly one low (1, 2, 3), one middle (4, 5, 6), and one high (7, 8, 9) digit. An orange entropic dot is treated as a two-cell line, in which the cells it connects contains digits that are not in the same group.

Links:

F-Puzzles
CTC