Guides › Mirrors: following a ray to the right target
Mirrors: following a ray to the right target
Published October 16, 2026.
In the Mirrors module, a ray leaves a source and crosses a grid 5 or 6 cells wide. Fixed mirrors deflect it; movable mirrors flip with a click. You must make the ray reach the right target.
The rules
Tap a movable mirror to flip it from « / » to « \ ». The ray is traced live: after each click you see the new route. The target to reach carries the symbol on the badge; the other targets, which are decoys, must not be hit. Then pull the lever: it is an attempt, so +15 seconds if the ray is not in the right place.
There is only one solution. In easy boxes two mirrors are movable; in medium and hard boxes, at least three.
How a mirror deflects the ray
A « / » mirror sends a ray that was going right upwards, and a ray that was going up to the right. A « \ » mirror sends a ray that was going right downwards, and one that was going down to the right. Just remember that « / » swaps right and up, left and down, whereas « \ » swaps right and down, left and up.
Method: work back from the target
A ray is reversible: if you trace it from the target to the source, it follows the same path backwards. Start from the wanted target, look at where the ray must come from, and find which movable mirrors must be in which position for it to reach the source. It is often faster than flipping at random.
Fixed mirrors do not move: they force certain passages. Spot them first, then set the movable ones one by one while watching the ray.
The usual traps
The first trap is flipping a mirror « to see »: the ray changes, but the new route is not necessarily better, and you lose the thread. The second is forgetting the decoy targets: a ray that hits another one is worth nothing, even if it also reaches the right one. The third is neglecting fixed mirrors, which impose passages that movable mirrors cannot undo.
When the ray seems to lead nowhere, start again from the source and follow it cell by cell with your finger: the live trace shows you where it stops.
Practise in the game
The game's tutorials, with no clock and no penalty, let you practise this subject: