A reasoning game about the three primary colours of light. Each puzzle is a light circuit: lamps at the top shine white or coloured light, which passes through filters in slots, diamond beam splitters and triangle prisms before reaching the crystals at the bottom. The tray holds exactly one filter per slot, and every filter must be used; put them in the right places so each crystal glows the colour of its outline.
There are just two rules. A filter only lets through the primaries it has (yellow = red + green, so it blocks blue), and a prism adds the primaries of two beams together (red + green = yellow). Splitters send the same light to two or even three crystals, so one filter can change several places at once. There are 5 chapters and 30 levels: First Filters, Coloured Lamps, Combining Prisms, Beam Splitters and Light Master, and each chapter also has endless random practice.
Every puzzle is generated by the game, which tries every way of placing the tray to make sure there is exactly one answer (filters sitting next to each other on the same beam can swap, so they count as one). Each colour also carries primary marks, circle = red, triangle = green, square = blue, so players who find colours hard to tell apart can reason with shapes.
How to play
- Tap "Play", or pick a chapter and level from "Levels". The first time you open a chapter, a "Lab notes" card explains the new rule; tap the book button any time to read it again, along with a chart of every colour and its primary marks.
- The outline and the label under each crystal show the colour it wants; the inside shows the light reaching it right now.
- Drag a filter from the tray onto a slot, or tap a filter and then a slot. The light changes at once, and a crystal that is right gets a tick and a chime. Tap a placed filter to pick it up and move it, or send it back to the tray.
- Work back from the crystal you are surest about: which primaries are left after each filter, and what does a prism add? The filters left in the tray are clues too.
- A wrong placement is never a fail: undo or clear the board any time. If you are stuck, "Hint" puts one filter in the right place (taking a wrong one back to the tray first if needed). No hints earns 3 stars, one hint 2, more hints 1. Clearing 4 levels of a chapter opens the next.
Controls
- Phone / tablet: drag a filter from the tray at the bottom onto a slot in the light circuit, or tap a filter and then a slot. Tap a placed filter to pick it up, then tap another slot to move or swap it, or the same slot to send it back.
- Mouse: drag filters, or click a filter and then a slot.
- Keyboard: keys 1–6 pick a filter from the tray, arrow keys move between slots and the tray, Enter or Space places; Z undo, H hint, M mute, Esc cancel the selection or go back to the menu.
For parents
- Made mainly for ages 13 and up, and 9–12-year-olds can start from Chapter 1. It turns the three primary colours of light from school science into hands-on puzzles: a filter keeps what two colours share, a prism combines them. Players juggle several conditions at once, reason backwards from the result, and use the "every filter must be used" rule to rule things out, which builds logical and systematic thinking.
- There is no timer and there are no lives. A wrong placement only changes the colour of the light, and you can undo or clear any time; a hint places just one filter instead of giving the whole answer away. Every colour also has shape marks (circle = red, triangle = green, square = blue) for players with colour-vision differences. Everything is light, glass and crystals, with no violence, scary content or gambling.
- No chat, in-app purchases, ads, outbound links or online leaderboards, and no personal details are ever asked for. Stars, seen chapter notes and the mute setting are stored only in this device's browser, and the game also works offline.
