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Laser Mirrors

Turn the mirrors so every crystal lights up at once.

🤔 How to play

  1. Lasers fire beams of light along the bench. Light every crystal at the same time to solve the level.
  2. Tap a mirror on a yellow turntable to turn it: it flips between / and \. Grey pieces bolted to the bench never move.
  3. Blocks and the lasers themselves stop a beam, and a crystal soaks up the light that lights it. Beams pass straight through each other.
  4. Splitters (striped see-through glass) let a beam through and reflect it, so one beam becomes two. A double crystal, with a ring of two beads, needs beams from two different sides.
  5. In the last group the lasers are red and blue. A red crystal needs red light only, and a blue crystal blue only. Red and blue light together make purple, which is just what a purple crystal needs.

Angle in = angle out

The law of reflection Left: a beam hits a flat mirror and leaves at the same angle to the dashed normal line as it arrived. Right: seen from above, a beam heading right turns up at a / mirror and down at a \ mirror. normal in out angle in = angle out / turns it up \ turns it down
Light leaves a mirror at the same angle it arrives, measured from the normal.

When light bounces off a mirror, it leaves at the same angle it arrived at, measured from the normal: a line at right angles to the mirror. That's the law of reflection. On this bench every mirror sits at 45° to the beams, so each one turns the light through exactly 90°. Which way it turns depends on which diagonal the mirror is on, so plan the whole route from laser to crystal before you start turning.

Tap a turnable piece, or press ← → to step through them and ↑ ↓ to change row, then Enter or Space to turn it. Z undoes, R resets and H or 💡 names a piece to turn. Drag the bench to look round it. Squares are named like a spreadsheet (A1 is the far left corner), so messages and hints can say exactly where a piece is. Every level has been checked by computer: each one can be solved, and only one setting of the pieces that matter works. Nothing is saved: ticks for solved levels last only this visit.

What it practises

The law of reflection, and the spatial reasoning to follow a beam through several bounces in your head. Later levels need real deduction: working backwards from each crystal, sharing a mirror between two beams, and mixing coloured light (red and blue make purple).