About Light Beams

A lamp shines across a dark grid full of mirrors. Tap a mirror and it swings round, from / to \ and back, sending the light off another way. Somewhere on the board are crystals, dull until light runs through them. Turn the mirrors so that every crystal is glowing at once and the puzzle is solved.

Light carries straight on through a crystal, so one beam can light several if you steer it well. Stone blocks stop it dead; bolted mirrors cannot be turned and have to be worked round; and from Medium up there are half-mirrors, drawn dashed, which let light through and reflect it at the same time, splitting one beam into two. Hard boards have two lamps. Not every mirror is on the light's way — some are there to tempt you.

Every puzzle is dealt from a seed and then checked by trying every way its mirrors can be turned, so it can always be solved and the par — the fewest taps that do it — is exact. Match par for three stars. The daily puzzle is the same for everyone and ranks the day by taps, then time; a hint shows a mirror worth turning, for thirty seconds.

Tips to win

• Follow the light from the lamp and find the first place it goes wrong
• Work backwards from a crystal: which mirrors could send light through it?
• A mirror the light never touches doesn't matter yet — leave it alone
• Every tap counts, so think before you turn: two taps on one mirror just put it back