Fill the grid so that every row, column, and box contains the digits 1-7, one / mirror and one \ mirror. Each clue shines a beam of light into the grid that travels straight horizontally or vertically and reflects off of mirrors. For example, a beam entering a / mirror from the left would leave going upwards. Clue values give the sum of digits along the beam until it leaves the grid. The ?s may be any digit except 0.