Draw a closed loop along the dotted lines that uses each grid point at most once. The loop must pass through all marked grid points. Traveling along the loop, in each grid point marked + the loop must turn left and in each grid point marked × the loop must turn right. To find out in which direction to travel is part of the puzzle.
(Rules and Example from WPC 2019 IB)
History of the puzzle
Invented by Gabi Penn-Karras (Germany) in 2011. First puzzle is on LMD portal under the name "Der Rundweg des Elbschiffers" (namely "The loop of the Elbe sailor").
Appearances on the past WPCs
- WPC 2019/Round 2 by Gabi Penn-Karras