The logic puzzle web site at which I have spent most time over the last few years is the wonderful Croco-Puzzle, produced by Bernhard Seckinger of Hilden, which is just south-east of Dusseldorf in western Germany. While there is a shop on the site selling additional puzzles and online puzzle magazines, there’s plenty of puzzles to solve for free.

The site is a world-class example of its type; however, it’s all written in the German language. Accordingly, here is an English-language walk-through, accurate as of April 2014. The write-up is in several sections, according to what you want to do at the site.