Laser & Mirror — free browser game

An optics puzzle: you have to guide the beam from the laser source on one edge of the grid to all of the star targets on the board by placing mirrors in the right spots. Clicking an empty cell places a mirror in the / orientation; clicking the same cell again rotates the mirror to the \ orientation; a third click removes the mirror entirely. Thanks to this three-click cycle you can place, rotate and delete with a single hand quickly. Mirrors reflect the beam 90 degrees according to physical optics rules: a / mirror turns a beam going right into up, up into right, left into down, and down into left; a \ mirror turns right into down, down into right, left into up, and up into left. Once you're sure you've placed all your mirrors, press the 'Fire' button; the beam's path is drawn with an animation, every star it hits lights up, and if all the stars are struck you advance to the next level. There are 7 levels in total and each is more complex than the last — the number of stars grows, obstacle walls are added, and intricate designs appear where a single beam must pass through several stars. Strategy: first mark the beam's starting direction and the position of the last star, then work backwards to figure out where the final mirror needs to be. If there are several stars, picture a single 'zigzag' path that can run one beam through them all in one go; rather than making two separate paths, one complex path usually solves it with fewer mirrors. The order of the mirrors matters, because when the beam strikes a mirror it changes direction and the mirrors after it are only affected along this new direction.