Hidato sounds as Japanese as Sudoku, but it is actually a game developed by Dr. Gyora Benedek, an Israeli mathematician. Just as Sudoku, though, Hidato is logic-based and not per definition a math puzzle.
Small Grid Hidato Puzzles with Answers
7 by 7 Hidato Puzzles with Answers
8 by 8 Hidato Puzzles with Answers
9 by 9 Hidato Puzzles with Answers
More Challenging Hidato Puzzles with Answers
Difficult Hidato Puzzles with Answers
Odd Shaped Hidato Puzzles with Answers
The rules of Hidato are, as with Sudoku, fairly simple. The goal of Hidato is to fill a certain grid with numbers. These numbers have to connect horizontally, vertically, or diagonally. The highest and smallest numbers are clearly stated and depending on the difficulty level, some numbers are already printed on the grid. It's said that every puzzle has a unique solution. Hidato grids can come in many forms and shapes.
We have created loads of puzzles based on the Hidato principle. Connect numbers in order: horizontally, vertically or diagonally. We have puzzles in different difficulty levels suited for all ability levels. The puzzles are excellent teasers, warmers or rewards for math students.
Here's a great Youtube explanation video of a well-known online Hidato game:
The Numbrix puzzle is all about makin an unbreakable path using a starting and finishing number (the numbers in the circles).The rules are just as Hidato, with the only difference notbeing able to connnect them diagonally! Numbrix and Hidato are much alike and are both highly addictive math puzzles or games.
We found 2 other great sources for Hidato puzzles:

Hidato.com also offers Hidato books, with hundreds of puzzles at increasing difficulty levels, a smartphone, iPhone and PC application.
Here a youtube review of the Iphone application

EdHelper.com offers a printable version of this game. We found only this website that offers a real variety of printable versions of the game. The site edHelper.com, an educational website offers a very clear and useful printable version of the Hidato puzzle!
On their website you can determine the size of the grid and the difficulty level. Our experience with the Hidato puzzles of edHelper.com are very positive. Students really love these puzzles and always ask for more.
The only downside of the edHelper site is that you have to pay for a subscription. We believe it's only 20 dollars per year, but us teacher like things for free. For this money, however, you get access to an enormous and extraordinary complete arsenal of math, science and English material. The edHelper.com website is, arguably, the most complete and useful educational website out there!
That said, Hidato played as online video game or printable used in the classroom or at home is a very engaging skill builder . Who said that learning can't be fun?
Here's an example of a printable Hidato puzzle (from Facebook Hidoku Puzzle Site):