Place the given tetrominoes in the grid using each of them exactly once. They can be rotated but not mirrored. Digits in the grid show the amount of occupied cells in the neighboring squares. Tetrominoes cannot touch each other, not even diagonally.
Grid control: Click the mouse button at the selected cell to change the color of the cell. You can also click on the given tetromino figures to mark them out. More details about grid control are at the help page.