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December 3, 2014 11:31 AM

Instant logic puzzles of customizable difficulty.

Once you've warmed up, try your hand at the great-granddaddy of the genre: the infamous Zebra Puzzle.

posted by Iridic (50 comments total)

Shared. Thanks for posting.
posted by josher71 at 11:33 AM on December 3, 2014 [1 favorite]

A good site for people studying for the LSAT!
posted by (Arsenio) Hall and (Warren) Oates at 11:39 AM on December 3, 2014 [2 favorites]

The only reason to learn to program in Prolog.
posted by GuyZero at 11:45 AM on December 3, 2014 [6 favorites]

1) I have an inordinate amount of love for logic puzzles, so thank you for sharing.
2) My neighbor had the Zebra Puzzle growing up, and I didn't know it had a name until now. I credit it with teaching me cigarette brands, something every small child should know.
posted by pitrified at 11:53 AM on December 3, 2014 [1 favorite]

I love love love this style of logic puzzle. Great find.
posted by solotoro at 11:54 AM on December 3, 2014

Prolog code for zebra puzzle
posted by el io at 11:54 AM on December 3, 2014 [5 favorites]

This is the best thing ever. I used to devour these things in puzzle magazines as a kid.
posted by jbickers at 12:16 PM on December 3, 2014

Awesome, thanks!

Puzzles.com also has a good archive of interactive logic puzzles. They haven't updated in ages so this will fill the void.
posted by Flannery Culp at 12:16 PM on December 3, 2014

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That's the urinal quiz right? The answer is use the stall?
posted by Ogre Lawless at 12:21 PM on December 3, 2014 [8 favorites]

This is great! I need some new way to procrastinate and this is perfect!
posted by TedW at 12:24 PM on December 3, 2014

That's the urinal quiz right?

Close! It's a diagram from a second year orthodontics exam.
posted by Iridic at 12:26 PM on December 3, 2014

I refuse to believe the number of people who have solved the Zebra Puzzle is small, since it's just a reductive logical game with no tricks (that is, no clever interpretations of the wording are needed, nor useful).

I did it as a kid, at least twice. Surely I'm not that unusually good at these puzzles.
posted by IAmBroom at 12:27 PM on December 3, 2014 [1 favorite]

I suck at these but I think they're so fun!
posted by Carillon at 12:36 PM on December 3, 2014

The number of favorites this post received is 3 less than a post submitted in the last hour that is not mathowie's post.
posted by joelf at 12:37 PM on December 3, 2014 [8 favorites]

I loooooove these! Yay!
posted by mochapickle at 12:44 PM on December 3, 2014

I loved these as a kid in puzzle books; I thought they granted you some sort of super power because they were so hard, but with enough concentration (and maybe a hint or two from my dad) you could finish 'em. Love this post!
posted by missmary6 at 12:50 PM on December 3, 2014

I typically love these in magazines, but for some reason these randomly generated ones seem completely opaque to me, even on "easy." Maybe my brain is fried...
posted by sonic meat machine at 12:51 PM on December 3, 2014 [1 favorite]

I loathe these puzzles. I despise them. Back in school I was in this "gifted" special class thing for kids who were too weird/bored during regular lessons. We did a lot of fun things in that class, like reading and discussing the Narnia series, and making animations on an Apple II. But we also did a bunch of these logic puzzles, and even then I was like "this is so tedious... can't I just write a computer program that can solve these for me?"
posted by sixohsix at 12:55 PM on December 3, 2014

I love these puzzles SO MUCH and have done since I was a little kid. Thank you for providing me with a more or less infinite source!
posted by sciatrix at 1:10 PM on December 3, 2014

Oh man, I loved these back when I was tutoring for the LSAT. Students either loved them or hated them with a passion. I understand that they are no longer on the LSAT though, is that the case?
posted by Rock Steady at 1:14 PM on December 3, 2014

Yeah I tutored the LSAT too. Basically by showing people how to do these puzzles, you could help them raise their scores quite a lot. Of course that made it obvious to me that a high LSAT score was kind of a dumb predictor of law school aptitude.
posted by freecellwizard at 1:17 PM on December 3, 2014 [1 favorite]

I always figured that knowing how to game the system with largely irrelevant info was pretty important for lawyers-to-be.
posted by Rock Steady at 1:23 PM on December 3, 2014 [4 favorites]

I also love these puzzles and can spend hours doing them, so, um, my job thanks you a lot.
posted by jeather at 1:27 PM on December 3, 2014 [1 favorite]

Protip (in reference to the 3x4 on challenging mode): Don't ever use the bottom set of check boxes, and when you come to the either-or clue, just pick one. It's faster to discover that you picked incorrectly and redo the last few steps then it is to solve it with 100% accuracy the first time.
posted by nzero at 1:43 PM on December 3, 2014

Man, I love these - always have. Thank you! Years ago I played a cheesy looking logic puzzle game called Sherlock (and another by the same company, Dinner with Moriarty). I recently discovered those are out for the ipad, and now I can use my fancy 'spensive to play cheesy 80's style games that never get old. Now I have a new source, so yay!
posted by routergirl at 1:44 PM on December 3, 2014 [1 favorite]

I refuse to believe the number of people who have solved the Zebra Puzzle is small...

Do you know what really killed Einstein? It was the Zebra Puzzle.

Did you ever wonder why Marilyn vos Savant hasn't aged since 2002? That's the power of the Zebra Puzzle at work.

Do you know why Will Shortz only has one eye? And why he wears an eyepatch over that one good eye, leaving his ruined socket bare to the world? Zebra Puzzle.
posted by Iridic at 1:47 PM on December 3, 2014 [4 favorites]

routergirl, thank you so much! I loved those games back in the day. I had no idea who their creators were, let alone that they had gotten an app out. Installing it now!
posted by daelin at 1:49 PM on December 3, 2014 [1 favorite]

Iridic: Do you know what really killed Einstein? It was the Zebra Puzzle.

Did you ever wonder why Marilyn vos Savant hasn't aged since 2002? That's the power of the Zebra Puzzle at work.

Do you know why Will Shortz only has one eye? And why he wears an eyepatch over that one good eye, leaving his ruined socket bare to the world? Zebra Puzzle.

(goes into hiding; glues fake mustache over real one; affects a vaguely Middle Eastern/Russian accent and a limp)
posted by IAmBroom at 2:06 PM on December 3, 2014 [5 favorites]

I understand that they are no longer on the LSAT though, is that the case?

No, still on there.

by showing people how to do these puzzles, you could help them raise their scores quite a lot. Of course that made it obvious to me that a high LSAT score was kind of a dumb predictor of law school aptitude.

The LSAT is a decent predictor of future performance, including performance in law school. There are quite a few studies to back this up.
posted by (Arsenio) Hall and (Warren) Oates at 2:33 PM on December 3, 2014 [2 favorites]

Now I'm annoyed. When they say that the cake shaped like a french horn is either the one with purple icing or the one with 27 candles, they actually mean "but not both", which is usually not the case (or is considered inclusive unless it is specifically marked out). Grumble.
posted by jeather at 3:17 PM on December 3, 2014

Yeah the 'or' in these puzzles is always exclusive or. Just think of it as one of those rules that you just have to know, like how "in disarray" in a cryptic crossword puzzle means it's an anagram.
posted by tractorfeed at 3:54 PM on December 3, 2014 [2 favorites]

I also love the Sherlock app, and find Honeycomb Hotel by the same developer to be super satisfying, too. Would rec.
posted by MeghanC at 3:58 PM on December 3, 2014 [1 favorite]

I remember being really bad at these when I was a kid, but now I'm... still pretty bad at them.
posted by Green Winnebago at 4:36 PM on December 3, 2014

Love these. Wrote a massive one (five items each in seven categories, 22 clues) for a puzzle-hunt once. Now you've put the notion in my head of coding a generator...
posted by rifflesby at 5:00 PM on December 3, 2014

I feel like I used to be pretty good at these, but apparently, not any more. At all. I keep trying, though, and sometimes I manage to get it. But that's pretty fleeting.
posted by darksong at 6:00 PM on December 3, 2014 [1 favorite]

I used to remember the deductive rules for how information migrates from one square to the others, but it's now misplaced.
posted by pwnguin at 6:23 PM on December 3, 2014

The important one I remember off the top of my head is that, once you know A = B, you know that everything not-A is also not-B, and vice-versa. That usually gets you a lot of extra X's in the grid.
posted by rifflesby at 7:06 PM on December 3, 2014 [1 favorite]

I adore these - to the point yhat, whenever I go on a trip, I buy a magazine full of them.
posted by spinifex23 at 11:17 PM on December 3, 2014

Very late edit - Dinner with Moriarty is not out for IOS, though I wish it were. I think the Honeycomb Hotel may be - here's the site.
posted by routergirl at 6:32 AM on December 4, 2014

I'm assuming that the people who do these in 30 seconds are just randomly filling in boxes and getting lucky? I mean you could barely click all the boxes in that time!

And what are the actual techniques for doing these things? Because I really, really suck at them. I get about halfway through and go, nope, there is no more information that can be gleaned from those statements.
posted by Naberius at 7:03 AM on December 4, 2014

The only reason I almost went to law school is because I enjoyed doing these so much and therefore knew I would get pretty LSAT scores. (I actually did but didn't do anything with them.)

God, if I could be a professional test taker, I think I'd be the happiest person in the world.
posted by MCMikeNamara at 7:06 AM on December 4, 2014 [5 favorites]

Naberius, there is a hint function on that site, and testing it out looks like it's quite useful. (The Kaser games -- Dinner with Moriarty etc -- also have similar functionality, though the puzzles are different.) The logic puzzle magazines also give step by step solutions so you can just get the one next thing you missed.
posted by jeather at 7:10 AM on December 4, 2014

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While entertaining, these puzzles have about a much to do with logic as sudoku has to do with math -- which is to say, not much.

Once you learn a few tricks of how certain phrases of language translate to a rote checkmark procedure, you can pretty much can do these puzzles half asleep like sudoku. If this is how they use the LSAT to decide who would be a good lawyer, it certainly explains a lot.
posted by JackFlash at 10:26 AM on December 4, 2014 [1 favorite]

JackFlash: "While entertaining, these puzzles have about a much to do with logic as sudoku has to do with math -- which is to say, not much.

Once you learn a few tricks of how certain phrases of language translate to a rote checkmark procedure, you can pretty much can do these puzzles half asleep like sudoku."

I...guess? After practicing and figuring out the little tricks, I've gotten much faster, and don't use a ton of logic now. But the way I figured out all the little tricks was through thinking about the logic.
posted by Bugbread at 6:47 PM on December 4, 2014 [2 favorites]

I can't decide whether I love you or hate you.
posted by insectosaurus at 8:13 PM on December 4, 2014

While entertaining, these puzzles have about a much to do with logic as sudoku has to do with math -- which is to say, not much.

Once you learn a few tricks of how certain phrases of language translate to a rote checkmark procedure, you can pretty much can do these puzzles half asleep like sudoku. If this is how they use the LSAT to decide who would be a good lawyer, it certainly explains a lot.

These is "just" elementary propositional logic. Learning how certain statements derive P or -P, if Q then R, etc., is learning how to use modus pollens, modus tollens, and other basic logical operations. It's not especially complicated logic, it's all stuff you'll learn in the first two weeks of a 100-level logic class, but it is logic.

And, by the way, sudoku doesn't have anything to do with math because it isn't trying to have anything to do with math, in the arithmetic sense. You will not perform a single arithmetic operation in sudoku. It uses numbers to represent exclusive truth values; it could, just as easily, use 9 letters of the alphabet and still operate exactly the same way, or 9 colors, or whatever. Sudoku is also a logic puzzle, basically the same as this stuff, because they're just truth tables where you're attempting to find the proposition that results in True given certain premises (values are exclusive to each other and within a given set). Given P or Q or R or S, if -P and -Q and -R, then S. If (P or Q) and -Q, then P. "Mr. Johnson lives on the corner of Elm and Cherry" and "The mansion belongs to either Mrs. Steele or the person who lives on Elm" reduces to (P and Q and R), S and (T or Q). It's all the same thing.
posted by Errant at 1:02 PM on December 10, 2014 [1 favorite]

Errant: "And, by the way, sudoku doesn't have anything to do with math because it isn't trying to have anything to do with math, in the arithmetic sense. You will not perform a single arithmetic operation in sudoku."

Clearly, then, KenKen (online) is the superior puzzle. Who doesn't enjoy a good application of the fundamental thereom of arithmetic?
posted by pwnguin at 12:25 AM on December 11, 2014

it could, just as easily, use ... 9 colors, or whatever.

Indeed you can (that was a favorite Xmas gift for my daughter a couple of years ago).
posted by TedW at 6:18 AM on December 12, 2014

pwnguin: Clearly, then, KenKen (online) is the superior puzzle. Who doesn't enjoy a good application of the fundamental thereom of arithmetic?

Commutativity?
posted by IAmBroom at 7:06 AM on December 12, 2014

subtraction and division are typically limited to to cells, which solves that particular ambiguity.
posted by pwnguin at 2:59 PM on December 12, 2014