Logic Masters Deutschland e.V.

Normal 4x4 Sudoku: Place the digits 1-4 exactly once in every row, column, and 2x2 box.

Skyscrapers: Digits in the grid represent skyscrapers, with their values corresponding to their heights. Taller skyscrapers obscure all shorter skyscrapers behind them. Clues outside the grid indicate the number of skyscrapers that can be seen in that row/column, from the line of sight of the clue.

Skyscraper Lines: A digit on a red circle indicates the number of visible skyscrapers along its line (not including itself) from that digit's direction of view on the line.

Clones: Gray squares contain exactly the same digit.