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Happy Puzzle Day!

January 29th, 2012

Happy National Puzzle Day!

The Jerry Slocum Mechanical Puzzle Collection is now online, featuring images from the collection of over 34,000 mechanical puzzles. This Dutch puzzle shoe from 1790 contains a hidden snuff compartment.

via MetaFilter


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Dinosaur Mazes are here!

January 27th, 2012

I’ve added two new collections of Dinosaur mazes to the puzzle collection, which are great for kids.

Each collection contains 50 booklets, with 12 mazes per booklet. Within each booklet, the mazes start out easier, and then get progressively harder.

If you’d like to see mazes in other shapes, let me know!

Easy Dinosaur Mazes

Not-so-easy Dinosaur Mazes

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Flickr Magick

January 11th, 2012

In the first few years of Flickr‘s existence, I made a lot of interesting composite images, using large quantities of Flickr photos, Perl, and the ImageMagick library. A few of these images have historical interest, illustrating the rapid growth of both Flickr and YouTube. This slideshow shows a few of these images, and provides descriptions of each slide.

Many of the techniques used to produce these slides can be found in my book, Flickr Hacks.

Enjoy!

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It takes 17 clues to make a Sudoku

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 have a unique solution.

link

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Lunch in the USA

January 8th, 2012

This is a Visualization of traffic on my Wheel of Lunch website. The wheel is often accessed around lunch time in the US, to find local restaurants. It only works in the US because it was easy to get working with ZIP codes, and I’m lazy.

This visualization shows the ZIP Codes that are being searched, over time, over a few days last December.

As each day progresses, the traffic tends to travel from right to left, starting in the eastern seaboard and ending in Hawaii.

You’ll notice a persistent number of hits that appear to be emanating from Fort Walton Beach, Florida. They all come from a single ZIP Code: 32547. This stumped me at first. I thought it might be a bot, but when I looked at the logs, I saw a bunch of frequent hits, from various IP addresses, with no real pattern to them. Searching “Wheel of Lunch 32547″ on Google, I discovered that this ZIP Code is associated with the entry for “Wheel of Lunch” on the StumbleUpon service. So those 32547 Florida hits mostly correspond to folks hitting the site from StumbleUpon, which is a significant source of traffic for the Wheel.

Remember: The Wheel knows where you live. Do not taunt the Wheel!

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Dumb Ripoff Alert

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 the text.

Interestingly, my original copyright notices are plastered throughout the entire book. The “author” apparently attempted to produce the book by using one or more of my PDF files as source to Amazon’s Digital Publishing program, but their text-processor eliminated all the puzzle graphics, resulting in a confusing jumble of numbers and krazydad copyright notices.

I only found out about this because somewhat bought the book, and asked me how to solve the strangely formatted puzzles.

I’m in the process of filing a copyright infringement notice, but feel free to post some amusing reviews on the Amazon page for your entertainment. I think I’m going to have to check to see if any of my puzzles have been more successfully ripped off. If you spot any other krazydad puzzles in the Kindle store, let me know!

UPDATE: Oh gee, I just found two more.

800-Tough-Sudoku-Puzzles by Naeem the Krazy Boy

The Super-Tough Sudoku Puzzles To Solve 800 Most Difficult And Extreme Sudoku Puzzles You Ever Gonna Solve In Your Life – Buy It Now – Red Hot Edition

UPDATE #2:

The number of these things is up to 912 now (that’s just from searching the Kindle store for “Sudoku 800″ and “Sudoku 1200″). Sigh… I have some paperwork to do this weekend, I guess…

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Hexadecimal Sudoku

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 next trip to the doctor’s office during this flu season, as it takes a lot longer to solve!

Enjoy!

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Fractal Music Box

December 13th, 2011

I made four of these laser cut music boxes as christmas gifts to my family. The pattern was generated with a Processing script, which I wrote. The lid contains an inlaid Hilbert space-filling curve. On each of the sides is a colorful J, representing each of my four family members (our names all begin with that letter).

The design for the box was generated with a Processing sketch that I wrote. You can get a copy of the sketch, as well as the plans for the box at Thingiverse.

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Sudoku Troubleshooter #4 – XYZ-Wing

November 24th, 2011

Troubleshooter #4: XYZ-Wing

This is part of a series on puzzle solving techniques. If you are stuck on a particular Krazydad puzzle, drop me a note, and I’ll use this space to help you out.

Michael wrote in an email:

Dad,
Good morning and an early happy thanksgiving. I really enjoy your puzzles and I have advanced to your tough ones now. I have been going through a bunch of them and I have a question for you. It seems like more recently you have been posting puzzles with no “logical” solution but that requires one to guess or work it out on the scratch pad. My question was is this a valid way of solving puzzles for you? As you will see I have gone through this puzzle attached and I can’t see a logical way to solve it. am I missing something here or do I just need to guess?

Here’s the puzzle that Michael got stuck on. This is a tough puzzle, book 85, puzzle #1. If you’d like to try it yourself, you’ll find it here:

In the next diagram, I’ve highlighed three cells which form an XYZ-Wing. XYZ-Wing is an advanced solving technique which is closely related to the more common XY-Wing, which I’ve covered in a previous column.

Take a look at cell D3, and the effect it has on cell F3.

If D3 is 4, then F3 can’t be 4.
If D3 is 5, then E1 must be 4, and F3 can’t be 4.
If D3 is 7, then A3 must be 4, and F3 can’t be 4.

Therefore, since this covers all the possible values for D3, F3 can’t ever be 4.

So we know that F3 must be 6. From here, the rest of the puzzle solves pretty easily.

As I said, this particular configuration, in which D3 contains XYZ, and E1 contains XZ, and A3 contains YZ, enabling us to eliminate Z from a 4th cell which is connected to all three cells, is called an XYZ-Wing.

It’s fairly rare, and only occurs in 8 of my tough puzzles, as compared to XY-Wing, which occurs 10 times more often. For the curious, the following puzzles contain an XYZ-Wing.

Book 25, puzzle 2
Book 42, puzzle 1
Book 55, puzzle 7
Book 56, puzzle 7
Book 62, puzzle 2
Book 71, puzzle 3
Book 85, puzzle 1
Book 93, puzzle 6

Happy solving!

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Campanello

November 21st, 2011

Campanello from David Watson on Vimeo.

Todd Kurt sent me the link to this very nice electro-mechanical doorbell, designed by David Watson. He provides detailed instructions on his website, along with a few other interesting projects.

I’m currently fascinated with such mechanisms, and hope to build something similar using a set of tuned desk bells I acquired a few months ago.

link

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