Lumen

Route the light. Mix it exactly.

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Map

Endless

Every puzzle is generated on the spot and checked for a solution before you see it.

Difficulty

Parts in play

Play a shared code

Daily puzzle

Last two weeks

Past puzzles count toward your stats and stars, but only puzzles solved on their own day keep a streak going.

Daily results are saved in this browser. Shared rankings are unavailable on this site.

Gallery

Stats & achievements

Backup

Progress is kept in this browser. Copy a save code to move it to another one. Restoring keeps the best of both.

How the puzzles are made

Built backwards. The generator starts from lasers, drops parts onto squares the light already reaches, and puts detectors where the light lands. Because the board is built from a working solution, every board can be solved.

Trimmed. Any part the solution doesn't need is removed. Then a solver looks for a cheaper answer; if it finds one, the board adopts it, so you never get a spare part.

Proven. The solver only considers squares that light reaches. It takes them in the order the beams arrive and either places a part or rules the square out for good, so each arrangement is checked once.

Hints that follow you. A hint first tries to finish the board you have built. Only if your parts can't lead anywhere does it fall back to the stored solution.

Lumen is plain HTML, CSS and JavaScript, with no libraries. Every sound is synthesised in the browser.

How to play

Light every detector. Each one needs an exact colour, and nothing extra.
Tap an empty square to place the selected part. Tap a part to turn it. Hold it, right-click it, or drag it off the board to take it back.
Mirrors turn a beam 90°. Splitters send it both ways: straight on and turned.
Light adds up. Detectors absorb whatever reaches them.
Stars count hints: none for three stars. Par is the fewest taps that solve the board; a ◆ on the map marks a board solved at par without a hint.

Parts on the bench

Laser Fires one colour in the direction it faces.
Detector The ring shows the colour it needs; the dots show which beams it still lacks.
Mirror Turns a beam 90°. Tap to flip it.
Splitter Sends light straight on and turned.
Gate Passes only its own colour. Chapter 5
White laser Red, green and blue in one beam. Chapter 6
Prism Red bends left, green goes straight, blue bends right. Chapter 6
Portal Light that enters one leaves its twin, same heading. A second pair is told apart by colour. Chapter 7
Pivot Bolted down. Tap to turn it; it costs no parts. Chapter 8

+= += += ++=

Keys: arrows move, Space places or turns, Delete removes, 1 and 2 pick a part, Z undo, Y redo, H hint.

Ambient music: soft pads that brighten as detectors light up

Language

Colour-blind aids: letters on detectors and lasers, and patterns on beams (green dashed, blue dotted)

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