Play Hidato Online
Fill every cell with consecutive numbers from 1 to N. Each number must be adjacent (including diagonally) to the next — creating a number snake through the grid!
Created by Brian Hamilton
Select a cell, then pick a number below
How to play Hidato
Fill every square so the numbers run 1, 2, 3 … up to the last one, with each number touching the next.
- Touching includes diagonals on a square grid — an inside square has eight onward moves.
- Every number appears exactly once, and every square is used.
- The given numbers cannot be changed.
- Every puzzle has exactly one solution.
Controls: tap a square and type a number, or tap a number then a square. Undo steps back and Check highlights mistakes.
Look for two clues two apart
Hidato asks for one thing: a chain from 1 to the last number where every number touches the next, diagonals included. Most people start at 1 and try to walk forwards, which is the slowest way to solve it. The numbers already on the grid are worth far more than the starting point.
The strongest move is to find two clues whose values differ by two. The number between them has to touch both, so it can only go where their neighbourhoods overlap — and that overlap is usually tiny.
Measured over 72 generated boards: these pairs appear 7.3 times per board and turned up on every single board. When one occurs, the square between is settled outright 53% of the time, and narrowed to just two candidates another 40%.
So before writing anything, scan the given numbers for pairs differing by two, then by three (a gap of two squares, still heavily constrained). That is where the board opens up.
Diagonals change everything
Hidato counts diagonal neighbours, which is easy to read past and changes the shape of the puzzle completely. A square in the middle of the grid has eight onward moves, not four.
| Square | Neighbours | Share of the grid |
|---|---|---|
| Corner | 3 | 8% |
| Edge | 5 | 41% |
| Interior | 8 | 51% |
The practical consequence is that corners are where the certainty is. A corner square has only three ways in or out, so if the chain must pass through one, its neighbours are nearly forced. Work the edges and corners before the open middle, where eight options mean almost nothing is settled.
The hexagonal board changes exactly this. A hex cell has six neighbours rather than eight, and every one of them is a proper side rather than a corner touch, so the chain is more constrained everywhere and the awkward diagonal step disappears. If the square grid's eight-way freedom feels loose, the beehive is the tighter puzzle.
A worked board
Notice how the given numbers cluster into runs with gaps between them. Each gap is a small separate problem: you know the number at each end and how many squares are missing, which fixes both the length of the detour and where it must start and finish.
Where solvers get stuck
Walking forward from 1. Starting at the beginning and guessing each next step is how the puzzle takes an hour. Fill the gaps between known clues instead; each is short and heavily constrained.
Forgetting the count has to match. If 20 and 25 are four squares apart on the grid but you have five numbers to place between them, the route has to wander — and if they are five apart with four numbers to place, it is impossible. Comparing the numeric gap with the physical distance rules out most routes immediately.
Leaving a square stranded. Every square gets used exactly once. A square that ends up with no unused neighbours, when the chain still has to reach it, means something earlier is wrong — and spotting that early saves undoing a lot of work.
Two things you can check about these puzzles
Every puzzle has exactly one solution. The board starts with every square revealed, and numbers are then removed one at a time — a removal is kept only when a solver confirms a single solution still remains, and put straight back otherwise. Because no step that would create a second answer is ever accepted, ambiguity cannot appear. 64 boards across every size, shape and difficulty were re-checked against a separate counter written from the rules alone; all 64 had exactly one solution.
Difficulty is how much of the chain is left showing. Easy leaves about 60% of the squares filled, Medium about 47% and Hard about 35%. That last figure is not a style choice: removal simply cannot go much below it, because a Hidato board with fewer numbers than that stops having a single solution at all.
Hidato, Hidoku and Numbrix
Hidato was invented by the Israeli mathematician Gyora Benedek, and the name comes from the Hebrew hida, meaning riddle. It also appears as Hidoku and, in a variant that allows only horizontal and vertical steps, as Numbrix, devised by Marilyn vos Savant.
Dropping the diagonals makes a surprisingly different puzzle: with four onward moves rather than eight, the chain is far more constrained and the solving feels closer to Numberlink. If you like following a single connected route under constraints, Slitherlink is the other end of the same family — one closed loop instead of one numbered chain.
More path puzzles
If you like drawing a route under constraints, try these: