The Mastermind
- Explorers
- Levels 1 and 2
- Cipher grid
The master thief’s own door, a Cipher Grid with just four runes. The hardest lock in the city. Fill each row, column and 2×2 quarter with 1–4.
Fill every row, column and 2 × 2 quarter with 1, 2, 3 and 4, each once.
This one comes back on . You can solve it then, signed in.
Last set on . The answer stays inside Kiwimath, and here is why.
What the board shows
- The grid gives four numbers and leaves 12 squares to fill.
- Among the given numbers, 1 once, 2 once, 3 once and 4 once.
What is a cipher grid?
A cipher grid is a 4 by 4 sudoku. Each row, each column and each of the four 2 by 2 quarters must hold 1, 2, 3 and 4 exactly once. There is no adding or taking away anywhere in it.
The numbers already printed are the clues. A well-made grid never needs a guess: every empty square can be worked out from the clues and the rule.
Children who like it often start talking in “because” sentences, which is exactly the habit that olympiad logic questions reward.
What it trains: Logic by elimination and keeping several rules in mind at once.
Puzzles like this are part of olympiad preparation from the first classes. See the plan for Class 1 or Class 3.
What to ask while your child works
Questions like these keep a child thinking without giving anything away. They work for every puzzle of this kind.
- Can you say the rule in your own words?
- Why did you put that number there?
- Did you check the new number against its row, its column and its quarter?
Warm up with one like The Mastermind
This warm-up is not the puzzle above, and its answer is below. It is a different puzzle of the same kind, made for this page, so your child can practise before The Mastermind comes back.
Fill every row, column and 2 × 2 quarter with 1, 2, 3 and 4, each once.
See the warm-up answer
The finished grid, row by row: 2 1 3 4; 4 3 1 2; 3 2 4 1; 1 4 2 3.
- The bottom-left quarter has 3 and 4, so it needs 1 and 2. The second column already has a 1, so the 1 goes in the bottom row and the 2 beside the 3.
- The top-left quarter has 2 and 1, so it needs 3 and 4. The first column has a 3 lower down, so the 4 goes first: the second row starts 4, 3.
- Now fill the right half row by row: the bottom row has 1, 4 and 3, so its gap is 2; the columns then fix the rest.
Questions parents ask about The Mastermind
When can my child solve The Mastermind?
The Mastermind is due back as the Explorers puzzle of the week on Saturday 31 October 2026, opening at 6 PM India time. Your child can solve it then, signed in, with hints that open one at a time.
Who is The Mastermind for?
It is an Explorers puzzle, for Levels 1 and 2, roughly Class 1 to 4. A younger child can try it with a grown-up reading the story aloud; the thinking matters more than the reading.