Here’s a practice puzzle for the other non-standard type on the Serbian GP this weekend, “Slitherlink Out-Liars” as they call it. I’m not too sure this one is representative of the type; certainly it feels different than the others I’ve solved.
Rules Draw a single loop that doesn’t touch or cross itself by connecting dots horizontally and vertically. Clues inside the loop indicate the number of adjacent edges used by the loop. Clues outside the loop indicate the number of adjacent edges used by the loop, plus or minus 1. Or see the instruction booklet.
Some more puzzles: 2010 German qualification. On croco puzzle: 2013-12-21, 2014-02-08, 2014-04-26. There was also one in the 2014 WPC.