Logic Masters Deutschland e.V.

Rules:

• Classic Sudoku: Every row, column and 3x3 box must contain every number from 1 to 9.
• Skyscrapers: 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.
• Sandwich Sums: A circled clue indicates the sum of the digits between 1 and 9 in the indicated row or column. Circled clues are also Skyscraper clues.

Play it online in SudokuPad.