- Turn the photo until you see the door or the corridor.
- On a computer: drag the thumbnail of the destination space (the “Où mène ce passage ?” strip: where does this way lead?) and drop it on the door.
- On a phone: tap the destination space, aim at the door with the cross, then “Poser ici” (place here).
- The way-back arrow is placed opposite, in the other space, marked “à placer” (to place). Tap “Placer les retours” (place the ways back): drag it onto the right door, or tap “C’est la bonne place” (this is the right spot).
- The counter of spaces reachable from the start tells you whether some spaces still can’t be reached.
Drag an arrow to move it. Undo (Ctrl+Z) reverses the last action.