This puzzle type appeared in 14th World Puzzle Championship in year 2005 in Eger, Hungry. This puzzle I made long back (may be after I come back from Eger after the championship in 2005)
Draw a single continuous loop in the grid using vertical and horizontal line segments such that the loop visits every square exactly once. The loop does not cross or overlap itself. It goes straight at every square with a circle. There is exactly one square between two consecutive circles that the loop visits where the loop does not make any turn.