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An advanced Kakuro technique

Wednesday, January 18th, 2017

I got a letter a few days ago, asking for help with a particularly intractable Kakuro puzzle: 8×8, Volume 14, Book 99, Puzzle #8. Since my Kakuro puzzles are arranged by difficulty, this is a particularly hard one, since it is in Book 99. Here you can see where the solver got stuck: I was […]

Serpentomino Puzzles for Christmas

Tuesday, December 13th, 2016

There’s a snake in my inbox! Bulgarian puzzle constructor Galen Ivanov sent me two collections of interesting new puzzles, Serpentominos, of his own design, which I’m passing on to you, as a Krazydad Christmas present. These puzzles share some characteristics with Pentominos, Dominos and similar mathematical recreations, and are quite different from the Sudoku and […]

Balance Quest Puzzles

Monday, August 4th, 2014

Whit McMahon, a puzzle constructor, wrote to me recently to share a new kind of puzzle he created last year called Balance Quest®. In these numeric logic puzzles, you fill in blanks so that the sum of each box is made by adding the numbers in the adjoining half-height boxes. Note that some of these […]

Masyu puzzles are here!

Friday, May 9th, 2014

I occasionally get requests to add new puzzle varieties to the collection. I have to ignore a lot of these, because there are 24 hours in a day. However, the last request I received, for Masyu puzzles, was hard to ignore, since I’ve enjoyed solving these myself for the past few years, and I’d love […]

Path Puzzles

Saturday, February 8th, 2014

Roderick Kimball wrote to tell me about an interesting logic puzzle he’s developed called Path Puzzles. In these puzzles, you must make a path that winds its way from one opening to another on the edge of the grid. The clue numbers tell you how many squares in each row or column are occupied by […]

Not a crossword

Thursday, August 8th, 2013

An interesting puzzle, basically a kind of maze with limited movements, that resembles a crossword, by Tyler Capp. Link.

Get started with Jigsaw Sudoku

Friday, September 7th, 2012

I recently added a new puzzle variety to Krazydad, called Jigsaw Sudokus. These are very similar to normal Sudokus. Like those puzzles, each row and column contain all the digits 1 through 9. However, these puzzles are missing the 3×3 blocks found in regular Sudoku. Instead, the puzzles are divided into a set of irregular […]

It takes 17 clues to make a Sudoku

Tuesday, January 10th, 2012

The science journal Nature reports that a mathematician has proven that it takes 17 clues to make a Sudoku. Gary McGuire of University College Dublin showed this in a proof posted online on January 1st (apparently he wasn’t partying on new year’s eve). This means that sudoku puzzles with 16 or fewer clues do not […]

Dumb Ripoff Alert

Friday, January 6th, 2012

I just found a book in the Kindle bookstore that (incompetently) rips off some of my sudoku puzzles. The book is called “The Most Difficult and Hardest Sudoku Puzzles” and is “copyrighted” by one Johnny Cohen. Here’s the cover: The cover helpfully informs you that the book is a BEST SELLER. Here’s a sample of […]

Hexadecimal Sudoku

Tuesday, December 20th, 2011

At the request of a few persistent (and possibly masochistic) puzzle fans, I’ve added four collections of Hexadecimal Sudoku to the puzzle collection. These are 16 x 16 puzzles that use the 16 hexadecimal digits (0-F), instead of the nine digits used in regular Sudoku puzzles. This is a good puzzle to take on your […]