Tap an empty cell on the beam to drop the part you have selected. Tapping the same cell again flips a mirror between its two diagonals, and a third tap takes it back into stock. Nothing is spent until you leave it there, so experimenting costs nothing. On a keyboard, 1, 2 and 3 pick the mirror, splitter and prism.

Forty-eight stages in four worlds of twelve: the Workshop, the Glasshouse, Prism Hall and the Observatory. Each world opens with a new part — the mirror, the splitter at stage 13, the prism at stage 25 and the turning mirror at stage 37.

It faces one diagonal or the other depending on how far the beam has travelled when it arrives. You cannot pick it up or turn it yourself — you change which way it faces by changing the route before it, making the beam run longer or shorter on the way.

That is a fog stage. The room starts hidden and every cell the beam touches, plus its neighbours, is revealed and stays revealed. Receivers and emitters are always visible, so you know the goal; the walls and absorbers in between are what you uncover.

An energy gate stays closed until the receiver it is wired to is lit. Get light into that receiver first; the gate opens on its own and the main path carries on through it.

The hint costs coins, or a short video when you are out of coins. It places the next correct part of a solution that keeps the parts you already placed. If one of your parts makes the stage unsolvable, the hint takes that part back or flips it instead. Using a hint caps that stage at two stars. Press H on a keyboard.

A wall simply stops the beam. An absorber, the dark pit with a violet rim, also stops it but sits where a promising line would otherwise continue, so it exists to kill the obvious answer. Neither can be moved.

Every stage gives you one more part than the shortest solution needs. Three stars means solving it without spending that spare, often by using a portal, glass block or bolted mirror the room already provides.

Yes. The stage button in the top corner, or L on a keyboard, opens the list of all four worlds with your stars in each. Any stage you have reached can be replayed, and finishing all forty-eight marks the campaign complete.

No. Every stage was checked by an exhaustive search over all legal placements before it shipped. If a stage is beating you it is hard, not broken.

Yes. Beamwork is completely free in your browser on ArcadeWhale. There is no purchase and no sign-up — open the page and start placing mirrors.

Yes. Your stars on every stage and your coins are stored on your device, so closing the tab does not reset you. You return to the first stage you have not finished.