Author: Andrey Bogdanov
Fill in the grid with numbers from 1 to 4 so that each row and column contains every number exactly twice. A clue outside the grid indicates the sum of all numbers between two Xs in the corresponding row or column, where X is the first number in that row or column from the direction of the clue.
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.