Author: Anurag Sahay
Insert a digit from 1 to 4 into every cell, so that each digit appears once in each row and column . Each digit in a cell represents the height of a building. Numbers outside the grid indicate either of two quantities - how many buildings of even height a distant observer could see or how many buildings of odd height a distant observer could see in that row or column (both quantities may have the same value). A building will hide any shorter buildings behind it. Clues are unlabeled - which skyscrapers they represent has to be determined as the puzzle is solved.
Grid control: Click at a cell reveals the value chooser. Click at the selected value changes the state of the cell. More details about grid control are at the help page.