I wanted to include a Latin square type puzzle, but many don't work that well with the digits 1-4. I needed a type that used empty squares to get a workable puzzle. Magic Snail seemed to fit the bill. I used to always have trouble with these puzzle. But since designing a few of these I got a bit more the hang of them. It's important to keep good track of the number through the outside few rows as the ordering forces a lot. It limits the placement of certain numbers in particular cells. This puzzle is not overly hard, although I accidentally sent it out with a missing clue at first. That made testing tricky. With the clue it's not the hardest.
Write the digits 1-4 once in every row and column (1-3 in the example). When traveling from the left top corner to the centre you should encounter the digits 1-4 four in order: 1-2-3-4-1-2-......-3-4.