Draw a closed loop along the dotted lines that uses each grid point at most once. The loop must go through all grid points with numbers. For each number, consider the two loop parts starting in that grid point. The number indicates the maximum length for which these loop parts are congruent.
(Rules and example from WPC 2019 IB)
History of the puzzle
Invented by Gabi Penn-Karras (Germany) in 2009. First appeared on LMD portal.
Appearances in the past WPCs
- WPC 2019/World Cup Round 2 by Jürgen Blume-Nienhaus