How to play Number Blocks
Fill each block of n squares with the numbers 1 to n, so that no two touching squares hold the same number. Also known as Block numbers, Number regions.
The rules
- The grid is divided into blocks outlined in bold.
- A block with n squares contains each number from 1 to n exactly once.
- Squares that touch — across a side or at a corner — never hold the same number (in the ‘sides only’ version, corners may touch).
- Given numbers can’t be changed.
Playing Number Blocks on Puzzle Solvers
- Choose whether numbers can’t touch at corners or only at sides, the biggest block, a size and a difficulty, then press New Puzzle.
- Tap a square, then a number on the pad (or type it). Use Notes (N, or Shift + number) to pencil in options.
- Clashes turn red as you go. Turn on Show block sizes for a reminder of each block’s size.
- Hint explains the next number — single squares, the only place left in a block, and numbers ruled out by touching.
Using the Number Blocks solver
- Choose the size, draw the blocks (or press Sample), then type the given numbers.
- Press Solve and step through: block sizes, single squares, the only place left, numbers ruled out by touching, pairs and what-ifs.
A worked example
A single-square block sits next to a block of two. The single square is 1, so the touching square of the two-block can’t be 1 — it’s 2.
The other square of the two-block must then be 1, which rules out 1 in all of its neighbours.
Strategies
- Single squares. A block of one square must be 1, so none of its eight neighbours can be 1.
- Two-square blocks. A block of two holds 1 and 2; any square touching both of them can be neither 1 nor 2.
- Only place. If a block’s 4 can only fit in one of its squares, put it there.
- Touching all of them. When a block’s number must go in one of a few squares, any outside square touching all of those can’t be that number.
- Big numbers are rare. Only big blocks have 5s and 6s, so look at those first when a big number is needed.
Common mistakes
- Forgetting that diagonal neighbours count as touching.
- Putting a 4 in a block of only three squares.
- Checking a number against its own block but not the blocks around it.
Where it comes from
This puzzle type was invented by the Japanese puzzle designer Naoki Inaba in the early 2000s and has become a favourite in European puzzle magazines.
Frequently asked questions
What does ‘sides only’ mean?
In that version, equal numbers may touch at a corner — only squares sharing a side must differ.
Is there always one answer?
Yes — every puzzle here is checked to have exactly one solution.
How big can the blocks be?
Up to 5 or 6 squares, depending on the option you choose.
How do I solve one from a magazine?
Open the Number Blocks Solver, draw the blocks, type the givens and press Solve.
Keep going
- Play Number Blocksa fresh puzzle every time
- Number Blocks Solverstep by step, every move explained
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