Every puzzle has exactly one answer, no digit appears twice in it, and the clues on screen are always enough to reach it for certain. So if you find yourself guessing, there is information on the board you have not used yet. This page is about finding it.
The method works on any Bulls and Cows style deduction puzzle, not just this one. New here? Read how to play first, because the method depends on reading each verdict precisely.
1. Spend the dead rows first
A row marked Nothing is correct removes three digits in a single read, and nothing else on the board is that efficient. Two of them on a ten digit keypad can leave just four digits in play: a much smaller puzzle than the one you started with.
Do this first, every time. The interesting-looking rows can wait.
2. Read the rows against each other
A row that says one number is correct is a statement about three digits together. Rule two of them out with other rows and the third is confirmed, without ever being named.
The first row kills the 4 and the 0, so the second is no longer ambiguous: the 5 is in the code, and not in the third slot. One row gave you a digit and a forbidden slot without naming either. No code ever needs a guess, only crossings like this one.
3. "Wrong place" is a position clue
Correct but in the wrong place tells you two things, and it is easy to take only one: the digit is in the code, and it is not in the slot this row shows. A row with nothing in the right place rules out a slot for every digit on it.
So once you know a digit is in the code, each of those rows takes a slot away from it. On a three digit code, two rows showing it in different slots pin it to the third. On five digit codes, where the Boss lives, these slot clues often decide the game.
4. Counts are exact
Verdicts are quantities, not hints. Two numbers are correct means exactly two, never "at least two", which makes the arithmetic usable:
- If a row scores two and one of its digits is dead, the other two are both in the code.
- If a row scores one and one of its digits is confirmed, the other two are out of the code, on every row.
- If your deductions ever contradict a row, one of them was wrong. Go back rather than forward.
5. Mark the board
The logic here is not the hard part. Holding six facts in your head while reading a seventh is, so mark as you go and let the board do the remembering.
- Tap a clue digit (click it, on a computer) to cross it off on that row. Tap again to circle it as confirmed.
- Hold a keypad digit (right-click it, or press Shift and the digit) to rule it out everywhere at once.
- Or switch on mark mode with the ✏️ button above the keypad. While it is lit, pressing a digit marks it instead of typing it.
6. Stuck? Re-read, don't guess
On three attempts a guess can cost you the round. If you cannot see the next step, re-read the dead rows: what you are missing is usually in a row you skimmed.
The Boss
Five digits, seven clues, every Wednesday and Sunday, and no more than two attempts. The method is the same and the margin is thin: work the dead rows, mark everything they kill, and only then read the scoring rows. Most Bosses have no Nothing is correct row, and then it plays like Hard Code on a bigger board.
Hard Code
No Nothing is correct row, so step 1 is gone and step 2 does the work. Find two rows that share a digit and read them against each other, and let the exact counts of step 4 settle the rest.