Colour Code

A hidden sequence of four symbols, drawn from six. You guess; the board tells you how many are exactly right and how many are the right symbol in the wrong place. It never tells you which. That gap is the whole game — every guess is a question, and the answer is two numbers you have to reason from.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Build a guess — ← and → move between the four slots; ↑ and ↓ cycle the symbol in the slot you are on. Z clears a slot.
3. Submit with Enter. A partial guess is refused, so a stray keypress never costs you one of your eight.
4. Read the feedback — the tick count is how many symbols are in exactly the right place; the triangle count is how many are correct symbols sitting in the wrong slot.
5. Deduce and repeat. Eight guesses, and each one should rule something out.

How do you play a code-breaking deduction game?

You guess a sequence and read the feedback as evidence rather than as a score. The two counts — exact matches and misplaced matches — tell you how much of your guess was right without telling you which parts, so a good second guess deliberately changes one thing at a time to isolate what the first guess proved. Eight guesses is comfortably enough if each one tests a hypothesis; it is not enough if you guess at random.

What is a good opening guess?

One that uses as few distinct symbols as possible — for example the same symbol in all four slots. It looks wasteful, but it answers a question no other guess answers as cleanly: exactly how many of that symbol are in the code. Two or three openings like that pin down the composition, and only then does position matter.

Does it really work offline?

Yes. Once the page has loaded once, the whole game — rules, board, feedback — is on your device. There is no server involved in play at any point, so it works on a plane, on the metro, or with the router unplugged. A CI test proves it by loading the game, stopping the server, and completing a full session.

Can I play it with a keyboard or a screen reader?

Both, fully. Every action has a key: arrows to move and change symbols, Enter to submit, Z to clear. The board publishes a parallel accessible description, so a screen reader announces each guess and its feedback in words — "two exact, one misplaced" — rather than reading out colours. Symbols are distinguished by shape as well as colour, so nothing depends on being able to tell hues apart.

Is there any money, betting or in-app purchase in this?

None, and there never will be. There is no currency, nothing to buy, no lives to refill and no wager of any kind. The suite deliberately stays entirely outside that category rather than near it.

Is the puzzle the same for everyone?

In practice mode, no — each game draws a fresh code. The daily puzzle is derived from the date itself rather than handed out by a server, so every player worldwide gets the identical board on a given day, and it still works if you are offline when the day turns over.

Six symbols, four positions, eight guesses — 1,296 possible codes, solvable in five guesses from any starting position with perfect play. Repeated symbols are allowed, which is what keeps the deduction interesting; forbidding them would shrink the space to 360 and turn the game into bookkeeping.

If you like reasoning from partial evidence, the regex tester and the JWT decoder scratch a similar itch with real data instead of symbols.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.