ref: 8a06ff26fc6abd77a4b4a08b839943f588d92dcf
dir: /html/pattern.html/
Pattern <p> Fill in the grid with a pattern of black and white squares, so that the numbers in each row and column match the lengths of consecutive runs of black squares. <p> Left-click in a square to mark it black; right-click (or hold Ctrl while left-clicking) to mark it white. Click and drag along a row or column to mark multiple squares black or white at once. Middle-click (or hold Shift while left-clicking) to return a square to grey (meaning undecided): dragging like that can erase a whole rectangle, not just a row or column.