The Numbrix puzzle was created by a woman named Marilyn vos Savant. In Numbrix, you fill in all the blanks of a grid so that there is a continuous chain of numbers between the start number, 1, and ending number. The only rule is that the numbers inserted must be done so vertically or horizontally, not diagonally. Another way to think of it is that you've won the game if you are able to take a pen and trace a vertical and horizontal path from one to the ending number.
Strategy approach (tips for completing Numbrix): You can fill in chunks of the grid that are easiest first, and then move to the harder areas. You do not have to start with the lowest numbers and end with the highest numbers. Numbrix creator, Marilyn vos Savant, says, "The easiest way (to complete the puzzle) is to scan from the lowest number to the highest one and fill in any missing numbers where the placement is certain. Repeat this again and again, though the missing numbers will become less and less apparent."
Have fun with Numbrix!