A closed loop that does not touch or cross itself must be drawn along the dashed lines. The numbers indicate how many times the loop makes contact with the numbered cell. A contact occurs when the loop reaches one of the corners of the numbered cell, and it ends only when the loop leads away from such a corner. Within a contact, the loop may travel on one or even several of the edges of the numbered cell!
(Rules and example from HCS 6)
History of the puzzle
First appeared on Hausigel Contest Series 6 in 2013. The puzzles were written by Roland Voigt (Germany).
Obviously, the inventor intended this as a Slitherlink variant, but this puzzle solves quite differently from normal Slitherlinks. The fact that Slitherlink is known in German as "Rundweg" which means simply "loop" may be one cause of the naming.
Hybrid with Slitherlink. First appeared on WPC 2019, written by Gabi Penn-Karras (Germany). The idea of some clues behaving as Touching Slitherlink clues and others as Slitherlink clues can be seen in "Doppelter Rundweg" (Double Loop) from German Nationals 2014, written by Nils Miehe (Germany).
Draw a closed loop along the dotted lines that uses each grid point at most once. Numbers that are inside the loop indicate how many edges of the respective cells are part of the loop, as in a standard Slitherlink. Numbers that are outside the loop indicate how often the loop visits the respective cells. In this context, a “visit” is defined as a contiguous section of the loop travelling on the boundary of the cell in question, including the possibility of just a single corner point; two such sections are considered separate visits if the loop leaves the boundary of the cell between them.
(Rules and example from WPC 2019 IB)
Appearances in the past WPCs
- WPC 2019/Round 8 (Standard / Touching Slitherlink) by Gabi Penn-Karras