Hidato / Numbrix Puzzle

One path, 1 to the end, no diagonals

Every cell in the grid holds a different number, from 1 up to however many cells there are, and consecutive numbers must sit next to each other. Up, down, left, right. Never diagonally, in the Numbrix style used here.

So the completed grid is one unbroken chain that visits every square exactly once. A handful of numbers are printed to anchor it, including the 1 and the final number, and the rest is deduction. There is precisely one way to join them, which means careful reasoning always gets there and guessing never has to.

How to actually solve one

Work outwards from what you already have. If a 7 and a 9 sit with a single empty cell touching both of them, that cell is an 8 and there is nothing to think about.

Then look for pairs of givens that are close together, because the path between two known numbers has a fixed length and the cells in between are far more constrained than they look. The other reliable move is the dead end: whenever a number has only one empty neighbour left, the next number in the sequence has to go there. Fill the forced cells, treat them as new anchors, rescan. Since every step is orthogonal you can always count squares to check whether two givens are even reachable in the number of moves available, which kills bad branches early.

Repeat until the chain closes. It always does.

Grid size and how much gets revealed

Grids run from 4×4 to 9×9 and start at 6×6. A 4×4 is sixteen cells and a five-minute puzzle. A 9×9 is eighty-one and an evening.

Difficulty controls how many numbers are printed for you: easy shows roughly 45% of the cells, medium about a third, hard around 22%. On a 9×9 that is the difference between thirty-six givens and eighteen, which changes the puzzle considerably more than the grid size does. A hard 6×6 is a harder sheet than an easy 9×9.

Every puzzle comes from a seed, so Generate New gives a fresh solvable grid each press. Thirty pupils can have thirty different sheets, or you can run one size and difficulty repeatedly to build a booklet.

Why they suit a wider range of solvers than Sudoku

There is no arithmetic here beyond counting. The rules fit in a sentence, so a six-year-old has them immediately, and yet a hard 9×9 will hold an adult for a while.

What the puzzle trains is sequencing and spatial reasoning, and the patience to fill in only what is forced rather than what looks likely. Sudoku asks you to reason about symbols that could be anything; here the numbers mean what they say, which is a much shorter route in for a child who finds abstract logic slippery. Teachers use them as starters, as calm-down activities, and as something to hand an early finisher that is not more of the same work.

Printing a set

Givens are shaded and bold on the puzzle page, so nobody wastes time working out which numbers were already there. The answer key is on by default and prints the full chain from 1 to the last number on a second page, which is as useful for demonstrating the method on a visualiser as it is for marking.

Add a title if the sheet is going into a folder. Add name and date fields if it is coming back to you. A4 or US Letter.