Logic Masters Deutschland e.V.

Usually I prefer sudokus with a short list of regularly used and easy to understand rules. This is not one of those puzzles. I've invented a new artifact rule that adds ambiguity to XV and visibility rules. I hope I've managed to justify its existence by the puzzle, and you're more puzzled by the logic involved than the interpretation of the rules. It's quite tricky and easy to make mistakes. Please read the rules carefully and check the 6x6 example image.

Rules

Normal sudoku rules apply.

Fog of war: The grid is covered with fog. There's one initial light source that illuminates the darkness. Place correct digits to get more light.

BYO killer / Nurikabe: Shade some cells to form a single orthogonally connected area. No 2x2 area is fully shaded. Each cell with a corner clue (number or ?) is unshaded, and each orthogonally connected unshaded area contains exactly one clue, which may occupy any position in the area. The digit in the clued cell gives the size of the unshaded area. The clue itself, if given, gives the sum of the area's digits. Digits may not repeat within the unshaded area.

Artifacts: Each row, column and 3x3 box contains one artifact. Artifact cells are shaded. Each digit 1-9 is artifact exactly once. Artifacts increase the value of the cell by an unspecified amount, which may be different for each artifact.

Visibility circles: Each circled cell is shaded and the value of the cell matches the total number of shaded cells visible in its own row and column combined (including itself), with unshaded cells blocking vision. Not all circles are necessarily given.

XV on area boundary with negative constraint: Values of cells joined by X sum to 10. Values of cells joined by V sum to 5. Additionally, one of each cell joined by X or V is shaded and unshaded. All possible X/V that cross shaded/unshaded boundaries are given.

Play this puzzle on CtC web app

6x6 Example

In the 6x6 example image below: green cells are shaded, orange cells are unshaded, and artifacts are marked with red circles. Try it out.

Clarification on Negative XV Constraint with Artifact Cells

I guess it would be easier to just say "negative X/V constraint need not apply with artifact cells", but that's not quite right. In order to be precise about the "all possible X/V" part of the rule, here's some corner cases in reference to 6x6 example.

On column 4 between digit 3 (unshaded) and digit 6 (artifact), there's no X clue. I could have put X clue there if I wanted, but negative constraint does not force artifact to increase the value of digit 6 by one.

In column 6 between digit 3 (artifact) and 2 (unshaded) there can't be a V clue. Artifact always increases the value of the cell by a positive amount greater than zero. Absence of V proves that 3 must be artifact.

On row 6 between digit 2 (artifact) and digit 5 (unshaded), the X clue is required by the constraint. The shape of shaded area tells that the cell R6C3 sees total of five shaded cells in its row and column and thus white visibility circle reveals that its value is 5.