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6 techniques to crack any code

Good codebreakers don't guess. They eliminate. These six habits turn a wall of clues into a short, satisfying chain of logic.

1. Start with “Nothing is correct”

Always read this clue first. It removes several digits from the board in one go, and every later clue gets simpler because of it. Cross those digits out in your head (or literally, on paper) before you look at anything else.

2. Re-read clues once digits are gone

A clue like “two numbers correct” on 2 0 6 is vague on its own. But if you already know one of those digits is out, the other two must both be in. Each elimination shrinks the remaining clues, so loop back through them.

3. “Wrongly placed” rules out a spot

When a digit is correct but wrongly placed, you learn two things: it is in the code, and it is not in that position. Note the forbidden spot. With two or three such clues about the same digit, its position is often forced.

4. “Well placed” is a fork

“One correct and well placed” means exactly one digit is locked in its spot, and the others are out. Usually you can't tell which digit yet, so treat it as an either/or and come back once other clues have removed one side of the fork.

5. Fill positions by pigeonhole

Codes never repeat digits. Once you know which digits are in the code, list where each one is not allowed. A digit with only one free spot goes there, which frees up the others. This is exactly how the Hard and Expert levels fall.

6. Check before you submit

Wrong guesses cost accuracy points. Before you tap the last cell, run your answer past every clue once. It takes five seconds and protects your first-try bonus.

Worked example: a 3-digit lock

Here's the Normal-level puzzle from the how to play guide:

1. Technique 1. “Nothing is correct” on 738 removes 7, 3 and 8.
   738NothingNothing is correct
2. Technique 2. 870 has one correct digit. 8 and 7 are out, so it must be 0. It's wrongly placed, so 0 is not in the third spot.
   870One wrong spotOne number is correct but wrongly placed
3. Technique 3. In 206, 0 sits in the middle and is wrongly placed, so 0 is not in the second spot either. The only spot left is the first: the code starts with 0.
   206Two wrong spotTwo numbers are correct but wrongly placed
4. Technique 4. 682 says one digit is in its exact spot. 8 is out, and the first spot belongs to 0, so it can't be 6. It must be 2 in the third spot, and 6 is out.
   682One correct & well placedOne number is correct and well placed
5. Technique 5. 614 has one correct digit, wrongly placed. 6 is out. If it were 1, it would have to avoid the middle, but the first and last spots are taken. So it's 4, and the only free spot is the middle.
   614One wrong spotOne number is correct but wrongly placed

Technique 6: check 042 against every clue. 682 ✔ (2 in place) · 614 ✔ (4 moved) · 206 ✔ (2 and 0 both moved) · 738 ✔ · 870 ✔ (0 moved). Submit with confidence.

Put it into practice

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