May 2010 Page 8 The Synapse utah.us.mensa.org Mental calisthenics Slitherlink satisfaction By Casey Harris I’d like to kick off this monthly review of the cool and fascinating in the world of self-enrichment (a more sophisticated term for “games and puzzles”) by introducing you to a puzzle known as Slither- link. This is a creation of Nikoli, a Japanese puzzle publisher who is most famous for introducing the Sudoku puzzle to the world. I’ve found this puzzle, which like Sudoku features numbers but is not really mathematical in nature, to be incredibly addicting and very satisfying to solve. It has a graphical element which allows you to see at a glance whether you’ve solved the puzzle correctly, and for that reason, Slitherlink is near the top of my favorites list. The goal of Slitherlink, like most of Nikoli’s puzzles, is simple: create a closed loop in the given puzzle grid which does not cross itself and which loop touches each numbered square in the grid on exactly the number of sides given in the number. There are not necessarily numbers given in each square, but those that do have numbers can only have one of four values: 0 (no sides of the square are part of the greater closed loop), 1, 2, or 3. A four in a square would indicate that all four sides of the box are used, which itself causes a closed loop and would violate the overall goal, so no 4’s are to be found in the grid. The process is simple: an x can be placed on each side of the numbered square that cannot be part of the overall closed loop (for starters, then, you can place an x on each side of every square with a 0 inside of it), and you can darken in the side of a square when you deduce that side must be filled. There are a few must-fill situations that you can come by with some experience and practice, but let me give you a few to get you started on the sample puzzles that follow: When you have: You can fill in: [Note: There is a more comprehensive tutorial on these puzzles on Nikoli’s website at www.nikoli.co.jp/en/puzzles/slitherlink/ , but this will get you started if you’re not near a computer.] Continued on next page utah.us.mensa.org The Synapse May 2010 Page 9 Slitherlink Continued from previous page With these rules in mind, you can set about using logic to see if you can complete the closed loop in these puzzles which follow, generously offered to our readership for free by Nikoli. The first one is an easy puzzle, and the second one is a medium-difficulty puzzle. The solutions to these puzzles are lo- cated on page 2 of this month’s The Synapse . [These puzzles are copyright Nikoli Co., Ltd., Japan, and are reprinted by kind permission. Please do not copy or republish without permission of Nikoli.] Puzzle 1 Puzzle 2 Hopefully, you’ve enjoyed working through these. Nikoli’s website has a selection of these puzzles free to try out (the electronic versions are a lot easier and more forgiving to work with than with pencil and paper), available at www.nikoli.com/en/ , and books full of its puzzles are for sale at Nikoli’s web- site or Barnes and Noble’s site at www.bn.com (search for “Nikoli”). I’m a fan, personally, of the ver- sion that was released in Japan for the Nintendo DS, “Puzzle Series Vol. 5: Slitherlink.” While it’s in Japanese, it’s relatively easy to navigate, and features the same solving tools as can be found on Ni- koli’s site. You can pick up a copy on eBay on occasion, or through specialty Japanese game distribu- tors on the Internet. Until next month, Happy Solving! .