Sources and verification
The reference: the app
The rules described on this site are those of the Code Breaker app, read from its code: clue calculation, levels, modes, row validation. When the app's built-in help and its code differ, the site follows the code.
Sources consulted
- Bulls and cows (new tab) (Wikipedia): the pencil-and-paper deduction game from which color-code games derive, and their history.
- Minimax algorithm (new tab) (Wikipedia): the idea of choosing the guess whose worst case leaves the fewest possibilities (Strategy page).
- Donald E. Knuth, article on the computer search for a four-peg color code, Journal of Recreational Mathematics, volume 9, number 1, 1976-1977 (Baywood Publishing): the reference article on the largest-remaining-group method; cited without a link and without its title, which contains the brand name of the original board game.
Links checked on October 30, 2026.
How the examples are verified
Before each release, two independent programs redo all of the site's calculations:
- a tool connected to the app's engine, without modifying it, plays each example game like a player: it places the pegs, validates each row and reads the clues calculated by the app;
- it counts the possible codes for each level and, after each guess, the codes still consistent with all the clues;
- it reads the challenge bounds over 10,000 random draws and the composition of Daily games;
- a second program, written separately, recalculates every clue, every count and every distribution, and blocks publication at the slightest discrepancy.
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