Amazon is selling this cool-looking speed cube for $5.21. I love the colors. I have been trying to solve Rubik's Cube for decades. I'll get it one day!

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Watch the video to make sure my summary here is right: You are in a dark room with a pile of coins. The coins have a silver side and a gold side. You know two things about the coins. There are hundreds coins. 20 of the coins are silver side up and the rest are gold side up. It's your job to make two piles of coins that have the same number of silver side up coins. The room is in total darkness and each coin feels the same on both coins.

This video says there in "a surprisingly easy solution." I haven't solved it yet but I have a pile of nickels and I'm going to give it a try.

[via Twisted Sifter] Read the rest

Here's the set up: two cars are side by side on the road. One car is going 70mph and the other is going 100mph. The drivers of the cars see a fallen tree in the road and start braking at the same time. The car that had been going 70mph stops right before touching the tree. How fast is the other car going when it hits the tree? The answer surprised me. Read the rest

Puzzle designer Fleb explains the rules for solving masyu logic puzzles, then solves one, explaining his logic. Read the rest

Puzzle designer Fleb shows how to solve a "cave puzzle," which is a logic puzzle that reminds me a bit of sudoku. It looks fun! Read the rest

If an entire 3x3 Rubik's Cube is too much, but a 2x2 one too plainly insulting, try this 2x3 one that you can get for about a fiver at Amazon. That's four ninths of a real Rubik's Cube for nine tenths of the price!

The product page assures you in its first bullet point that this puzzle contains "no fabrics." SOLD. Read the rest

This stunning line of geologically-inspired jigsaw puzzles, named Geode, is the creation of Massachusetts-based generative design studio and retailer Nervous System.

As described in their blog:

Geode is a jigsaw puzzle inspired by the formation of agate, a colorful banded stone. Each puzzle is unique, emerging from a computer simulation that creates natural variations in the shape, pieces, and image. Hundreds of lasercut plywood pieces intertwine to form a challenging, maze-like puzzle. Each geode is a slice of an algorithmic rock.

The puzzles are intricately cut in birch plywood, completely unique from each other, and available in two sizes (approx. 180 pieces for $60 and 370 pieces for $95). (My Modern Met) Read the rest

Fans of The Perplexus (one of my favorite puzzles) might be interested in Zenth, a 3D wooden labyrinth on Kickstarter. As in The Perplexus, the object is to guide a steel ball through a multiplanar labyrinth. In fact, the creator of Zenth was a student of the creator of The Perplexus, Michael McGinnis (who wrote an article for me about designing The Perplexus when I was editor-in-chief of Make).

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If you've ever tried to fold a fitted sheet, you probably know you can't just fold it like a regular sheet. If you are like me, you will just wad it up and hide your shameful attempt in the closet. Here's a woman made of better stuff than me, who has conquered the fitted sheet conundrum. The first video shows you how to fold a fitted sheet without elastic all around the edges, and the second video shows how to fold one with elastic all around the edges. Read the rest

Menseki meiro means "area mazes." It's a new puzzle genre that challenges you to derive the length or area of rectangles based on the given dimensions of neighboring rectangles. I got an advance copy of Area Mazes, with 100 puzzles. It's addictive. They start out easy. The later ones are very difficult.

Here are the rules:

Here's an easy one:

Here's a hard one:

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The Riddler has poisoned Catwoman. He tells Batman he can save her by giving her an antidote, which is in one of 1000 barrels in a room. The other 999 barrels have more poison. The Riddler will let Batman use his antidote detecting machine. What is the smallest number of tests he needs to conduct to guarantee he finds the antidote?

This is a cool stop-motion Lego video version of the poisoned wine problem I posted earlier this year:

You are a king and have invited 1,000 guests to a party. Each guest has brought one bottle of wine. But before any of the wine has been opened, your chief spy takes you aside and tells you that he is certain that one, and only one, bottle of wine contains a poison that will kill anyone who drinks even a drop. The poison takes one hour to kick in. The king has 10 prisoners he doesn't mind killing. How does he use them to identify the poison wine and get rid of the bottle (and the person who brought it) so he can get on with the party?

Puzzle designer Fleb takes a look at the Instant Insanity puzzle, which was patented in 1899. It reminds me of a cross between Rubik's Cube and sudoku.

I like Fleb's videos because he teaches you general principles of puzzle solving, not just how to solve a particular puzzle. Read the rest

A couple of days ago I mentioned the the MoYu YJ Lingpo 2 x 2 x 2 Speed Cube. I still haven't solved it, but I wanted to make a quick video to show how smooth it is. The little cubes rotate around a plastic sphere, and are connected by springs. It's practically impossible to jam it, unlike every other Rubik's Cube I've used. I thought it would be a snap to solve, having only 8 cubes (compared to the 27 26 cubes of a regular Rubik's cube) but it turns out I'm even dumber than I thought. I'm not giving up! Read the rest

I've never solved Rubik's Cube, but I've never seriously tried. One reason is that most of the cubes I've used are poorly made. They lock up when I try rotating a section, which is frustrating. I did a bit of research and was told to get the Moyu Weilong GTS2 ($15). It's a little smaller than the standard Rubik's Cube, which is a plus, because it's more comfortable to handle. And it's very smooth to turn, because of the rounded off interior corners. I also got the MoYu YJ Lingpo 2 x 2 x 2 Speed Cube, which I'm going to try to tackle first. Read the rest

Andre F. completes a 33,600 piece jigsaw puzzle called "Wildlife" by Educa. Dimension of the finished puzzle: 224.41 x 61.81 in. He spent a lot of time just turning the pieces right side up!

[via] Read the rest

Here's a good puzzle from Martin Gardner's Mathematical Circus. The book is out of print but used copies are cheap.

Problems involving weights and balance scales have been popular during the past few decades. Here is an unusual one invented by Paul Curry, who is well known in conjuring circles as an amateur magician

You have six weights. One pair is red, one pair white, one pair blue. In each pair one weight is a trifle heavier than the other but otherwise appears to be exactly like its mate. The three heavier weights (one of each color) all weigh the same. This is also true of the three lighter weights. In two separate weighings on a balance scale, how can you identify which is the heavier weight of each pair?

Our guest on the Cool Tools Show podcast this week is Adam Rubin. Adam is the New York Times best-selling author of Dragons Love Tacos, Robo-Sauce, and half a dozen other critically-acclaimed picture books. He is also a world-renowned inventor of illusions and was recently named Director of Puzzles and Games for ArtofPlay.com.

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Show notes:

Frixion Erasable Blue Gel Ink Pen ($13, 3 Pack) "So, this pen is not actually marketed as a disappearing ink pen. It’s marketed as a Frixion Pen, and its intention is to be an erasable pen — it’s a normal-looking pen and on the back of the pen is this sort of rubber or plastic nib. And if you write with the pen and you rub the nib over the ink, the ink goes away. But, the true nature of the pen is that it's heat activated. So, if you heat up the ink, it disappears. That could be with the nib that's on the back of the pen or that could be with the flame from a lighter or that could be in a microwave. So, basically, what you have, is you have a pen that writes with ink that you can make disappear with fire. And that is a pretty cool tool to me. … One of the cool things about it is that you can use it sort of as a fun science thing to do with kids because, you don’t necessarily need to use fire. Read the rest