Logic Masters Deutschland e.V.

• ISOFILL: Divide the grid into 9 regions, each with 9 orthogonally connected cells. Every cell in a region must contain the same digit. All of the digits 1-9 must appear in the grid.
• SKYSCRAPER: Each digit in the grid represents the height of a building in its cell, and taller buildings obstruct the view of shorter ones behind them: clues outside the grid give the number of buildings visible from that vantage point in the clue's row or column.
• The cell with a grey square is even.

Sudoku-Pad

Easier version with the same ruleset: Skyscraper Isofill (6x6)