Logic Masters Deutschland e.V.

Nurikabe: Shade some cells in the grid such that all shaded cells form a single connected region and no 2x2 square is fully shaded. Each unshaded region must contain exactly one clue cell.

Build-your-own X-Killer: Each unshaded region is an X-killer cage. Digits within the cage may not repeat and must sum to the total given in the corner of the clue cell. Additionally, the digit placed in the clue cell must equal the number of cells in the cage.

Odd: Cells with gray circles must contain odd digits.

f-puzzles: https://f-puzzles.com/?id=ycqauw7h
CTC: https://tinyurl.com/2p8dtxyv