Cipher is a free online Mastermind-style code-breaking puzzle — for fans of Mastermind and Wordle who enjoy deduction-feedback shapes. A secret sequence of colored pegs is hidden — your job is to deduce it within 10 guesses, no download required.
Cipher is not a plain Mastermind clone. Each game grants you a small bank of Probes — a limited deduction power-up shown in the HUD above the board.
Most Mastermind-style games on the web are straight ports: same rules, same beige board, and often the classic version's biggest ambiguity left intact — feedback pegs that new players misread as position hints. Cipher redesigns the experience around a dark spy-agency board with jewel-tone pegs and makes the feedback contract explicit: filled circles and outline circles are aggregate counts, never mapped to slots, which the on-page guide and FAQ spell out so you learn to treat each row as a numeric constraint instead of guessing at what the pegs mean. The Probe is the genuine mechanical departure — a limited power-up (one in Daily, two in Infinite) that reports how many still-hidden positions share a chosen slot's secret color, a count only, never the color. It costs no guess row and doesn't touch your streak or score, so it rewards knowing where to ask a question, which is a deduction skill classic Mastermind never tests.
The two modes are also tuned as different puzzles rather than difficulty labels. Daily is the disciplined version — 4 pegs from 6 colors with no duplicates, the same seeded code for every player worldwide, streak tracking that resets if you miss a day, and a (11 − attempts) × 100 score that makes a 3-guess solve worth eight times a 10-guess scrape. Infinite flips every constraint: 5 pegs, 8 colors, duplicates allowed — 32,768 possible codes — with your run score built from consecutive wins and submitted only when you finally lose. One mode is a shared daily ritual; the other is a survival ladder.
The code-breaking format Cipher builds on descends from Bulls and Cows, an old pencil-and-paper game where players deduced each other's secret numbers from exact-match and wrong-position clues. Mastermind itself was devised in 1970 by Mordecai Meirowitz, an Israeli postmaster and telecommunications expert, and became one of the best-selling board games of the 1970s — its colored pegs and hidden-code shield are still instantly recognizable. The game has since become a staple example in computer science and logic teaching, because the deduction it demands is pure information theory: every guess should be chosen to eliminate as many remaining codes as possible, not just to test one hypothesis. Cipher keeps that intellectual core intact and adds what a browser makes possible — a globally shared daily code from a date-seeded generator, automatic streaks, and the Probe.
After each guess, Cipher shows filled white pegs (exact position match) and outline white pegs (right color, wrong position) alongside the row. The feedback does not map positionally to your guess slots — just count the filled and outline pegs to narrow down possibilities.
Daily mode gives a 4-peg code with 6 distinct colors (no duplicates). One puzzle per calendar day, shared globally. Infinite mode uses a 5-peg code drawn from 8 colors with duplicates allowed — vastly harder with 32,768 possible codes.
Not in Daily mode — the 4 pegs always use 4 distinct colors. In Infinite mode duplicates are allowed; the feedback algorithm handles them correctly, allocating each color match only once.
The Probe is Cipher's signature power-up: 2 per game in Infinite, 1 in Daily. Tap PROBE, then click a peg position. Cipher reports how many of the still-hidden positions share that position's secret color — a count only, never the color itself. It is a deduction aid, not a giveaway. A Probe does not use a guess row, the remaining count shows in the HUD, and Probes reset each new game.
No. Probes are never persisted, so the once-per-day localStorage lock is untouched — a probed Daily still submits exactly once on first completion and scores by the normal (11 − attempts) × 100 formula. The Probe is a strategy aid, not an exploit.
The daily code uses a seeded RNG with a seed derived from the calendar date. The same date produces the same seed worldwide, so every player gets an identical puzzle regardless of timezone.
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