According to a recent post in the Flickr Blog the ‘favorite’ color of the Flickr community is a warm brownish taupe. The blog points to a nifty application, favcol which computes the average color of all the images on Flickr recently tagged ‘favcol’. In actuality, that brownish taupe color is what you tend to get […]

Kakuro Puzzles, for the uninitiated, are numeric crossword puzzles. If you like Sudoku, you will probably like Kakuro too — they both can be quite addictive. There is a collection of free kakuro puzzles in my puzzle section. Last year, I wrote three inexpensive Kakuro puzzle books for Ulysses Press. They can now be pre-ordered […]

Eduyng Castano writes to me about a Sudoku solving technique he has discovered. Here is his paper describing what he calls Golden Chains (pdf). The technique is a generalization of XY-Wing that identifies exclusion pairs connected by chains of arbitrary length. It solves many (but not all) of the same puzzles that can be solved […]

Puzzle Japan is the puzzle website for Nikoli, a popular puzzle publisher in Japan that popularized sudoku puzzles. Their website offers eight different logic puzzles, including sudoku and kakuro, available in online and printable formats. Many of the puzzles involve building walls or boundaries, an activity reminiscent of the game of Go. One of my […]

I’ve developed a new kind of puzzle which I’m calling a Krypto Kakuro. They combine elements of crossword puzzles, sudoku and cryptograms (or cryptarithms to be precise). Here are some samples for you to try. If you aren’t familiar with kakuro puzzles, I suggest you solve a few of those first, before tackling these puzzles, […]

If you like my sudoku puzzles, you’re gonna like my new kakuro puzzles. Also called Cross Sums, these puzzles are like a cross between a Sudoku and a crossword puzzle. I’ve been working on some software that generates these puzzles, and have published a set of them here at Krazydad. Each file contains 20 puzzles, […]

I’m working on creating more printable puzzles for the site, in addition to the sudoku puzzles. Here’s a collection of printable mazes, suitable for solving with a pencil. Perfect for a rainy day when you’ve got a bored kid in the house or office. The mazes come in 5 different difficulty levels, ranging from easy […]

Sudoku is a game of pure logical deduction, just like Kakuro and other Japanese number puzzles. Unlike games of luck such as card and bingo games, guessing is never required. I’ve now learned a number of methods for solving tough Sudoku puzzles by hand, including X-Wing, Swordfish, Jellyfish, Squirmbag, Turbot-fish, XY-Wing, XYZ-Wing, Conjugate Pairs, Bowman […]

Currently my sudoku software does a very crude job of estimating puzzle difficulty. There’s an especially wide range of difficulty levels in my “super tough” puzzles – some of them are pretty easy, others are genuinely “super tough.” My experience shows that most other computer programs do a pretty poor job at this too. The […]

Like seemingly everyone in LA, I have recently been bitten by the Sudoku bug, a craze which swept England last spring. The Los Angeles Times started publishing these puzzles a few weeks ago. Like many geeks, this addiction not only involves solving them with a pencil, but solving and generating them with a computer. I […]