Logic Masters Deutschland e.V.

Normal sudoku rules apply.

Yin-Yang: Shade some cells such that all shaded cells are orthogonally connected, all unshaded cells are orthogonally connected and no 2x2 area is completely shaded or unshaded.

Fortress: A digit in a shaded cell must be greater than all orthogonally connected unshaded digits.

Squares and circles are unshaded.
A digit in a square must be equal to the number of unshaded cells it sees in its row and column combined, including itself, where shaded cells block vision and are not seen.
A digit in a circle must be equal to the number of unshaded cells in the surrounding 9 cells including itself.

SudokuPad link