Ripple Effect is a nikoli puzzle that I read about a while back on su.doko.es.  The name gives you very little idea of what the puzzle is like, so here is a basic description.  The puzzle consists of a grid of any size divided into polyomino sections called rooms.  Each room must be filled with each of the digits from 1 to the number of squares in the room.  If a digit appears more than once in any row or column, they must be separated by a number of squares equal to the digit.

The nikoli page linked to by su.doku.es doesn’t have many examples of the puzzle, so I hunted around to find some puzzles to try out.  The first good set of puzzles that I found was here.

Enjoy!

Sudoku Tiger is a site that offers software for playing Sudoku, Killer Sudoku, and Hashiwokakero (here shortened to Hashi.)  The software is not free, but there are free puzzles of all of the featured kinds available on the site.

Of particular note is the solving guides for sudoku, killer sudoku, and hashiwokakero.  Sudoku solving guides are a little dime a dozen these days, but the it’s worth checking out the guide for hashiwokakero.

Su.Doku.Es recently posted an article about the Nikoli puzzle called Hitori. So, I figured it was a good opportunity to write about it. A Hitori puzzle presents a grid filled with numbers. To solve the puzzle, you need to black out numbers such that there is only one of each in every row and column. Sound familiar? There are a couple other constraints. Squares that are blacked out can’t be orthogonally adjacent to each other. Also, every square that is not blacked out must be orthoganally adjacent to at least one other square that is not blacked out. Here is an example of a Hitori puzzle from wikipedia.

If you’re interested in a collection of Hitori puzzles that you can play online, I suggest checking the Perplex City site.

Wei-Hwa Huang has a post on his blog about forming a Nikoli-like puzzle club in the US.  He’s looking to start a web site first before moving to print and he’s looking to find puzzle designers to help get the project off of the ground.

The New York Times ran an article today on Nikoli.  The most interesting part of the article is a discussion of why Nikoli is so successful.  Maki Kaji, who runs Nikoli, attributes their success to open forums that allow readers to submit criticisms for puzzles and post some of their own inventions.

Of course, the question that is sure to arise from all of this is:  “What’s going to be the next sudoku?“  And it’s a question that’s been asked for the past two years or so.  On the NYT site, they have three Nikoli puzzle types that you can play: Kakuro which I think would have exploded by now, if it were going to.  Nurikabe which both Wordstream and Mochikoro are derived from.  And Masyu which is an interesting loop drawing puzzle.  My prediction: None will be the next sudoku.

Thanks to zotmeister for this tip. Puzzle Japan is offering their nikoli style puzzles free for the entire month of July. To play them, go to the login page and enter pj for both the username and password. Puzzles available on the site include sudoku, kakuro, nurikabe, and others. Happy puzzling.

Here’s this week’s Mochikoro puzzle. A little late.

solution pdf

Here’s today’s Mochikoro puzzle:

pdf solution

This week a 19X19 puzzle.  My plan is to post five puzzles in this size and then take a break from mochikoro for a while to try other puzzles.

pdf solution

Here’s this week’s mochikoro puzzle.  The last puzzle that I will do in the 15X15 format.  Next week, expect a larger puzzle.

pdf solution

Hopefully this week’s puzzle has a unique solution.

pdf solution

I have updated last Monday’s Mochikoro puzzle such that it has a unique solution.  If you click over, you’ll see that it has changed.

Here’s my next mochikoro puzzle.

pdf solution

For today’s 15X15 mochikoro puzzle, I actually managed to have symmetrical clues.  I’m starting to realize, in making these puzzles, that single cell islands should only be placed in areas where removing one would create a 2X2 pool or break the chain of islands.

I’ve realized that people who haven’t been coming by since the first puzzle I put up probably don’t know the instructions for solving a mochikoro puzzle.  Instructions for puzzle solving are included in the pdf files that I make up.  You can also click the mochikoro tag below and read some of my earlier posts about this kind of puzzle.

And here’s this week’s puzzle:

pdf solution

This week’s mochikoro puzzle has a 15X15 grid. And I’m back to asymmetrical clues. (I tried.) The 15X15 format makes for a more difficult puzzle, both for solving and for creating. Enjoy!

pdf solution