Logic Masters Deutschland e.V.

Rules:

Normal Sudoku rules apply.

Skyscrapers: Each cell represents a skyscraper, with a height equal to its value. A clue outside the grid gives the number of skyscrapers visible in that row/column from the clue's end, where skyscrapers block the view of skyscrapers with the same or lower height behind them.

Doublers: Nine cells in the grid (one per row, column, and box) are doublers, which count as double their value for skyscraper heights. The doubler cells consist of a set of the digits 1-9.