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2011: Five Children

For several years now, I've been side-stepping the difficulty of buying my younger brother a Christmas present by designing him a puzzle hunt instead. This describes what I did for midwinter 2011-2012.

I'm going to occasionally put paragraphs in this style to designate "out-of-band" commentary.

Also, I'll use this style to designate narration -- these are story segments I read out loud during the hunt to drive it along.

Apologies in advance for not having more photographs of the proceedings.

This year's puzzle hunt was framed as a strange Christmas story. Let's begin:

This is a story of five remarkable children, and a rather odd set of Christmas presents.

It begins in late December, in a house in Southwest Michigan. Five siblings -- Ann, Bobby, Cliff, Dalia, and Emily are gathered together.

Ann begins the conversation, "I got a package from our Aunt last week; it contained five wrapped but unlabeled presents. I figured they were presents to all of us or something, so I just mixed them in under the tree."

"However, it seems I was wrong; this note came in the mail today."

"Well," said Dalia, "I guess we have to find the unlabeled boxes amidst all these other presents."

"Yeah," said Cliff, "then figure out which one is MINE!"

"Remember Cliff," said Emily in her quiet voice, "we have to all have our presents so we can open them in order of descending age."

After a bit of searching, Mike extracted five unlabeled presents from under the secular midwinter tree:

five presents

With the help of the note, he was able to connect them with the correct children and figure out the children's relative ages. (Those playing along at home will wish to know that the yarn-wrapped red box sounds fragile when shaken.)

Once Mike figured this out, the story continued:

"Well," huffed Bob, "that was exhausting. Let's see what we got!"

The children took turns opening their boxes and looked at the contents in surprise. Ann went first.

"How wonderful," said Ann, "I love dioramas!"

Then Bob opened his box.

"Yarn? I HATE yarn," fumed Bob.

"Fine by me; I'll do yours," said Cliff, grabbing at the box in Bob's hands.

"Keep off!" Bob slapped him back.

Cliff turned to his present in a sulk.

"It looks like I have to bake mine," grumbled Cliff. Then, perking up and grabbing and Emily's present "what did you get Emily? Want to trade?" Now shaking the box he exclaimed, "sounds fragile."

Ann convinced Cliff to return the box with a stern look.

Emily timidly peeled back the paper of her present.

"I think mine's broken," worried Emily.

"Don't worry, Em, think of it like a, uh, jigsaw puzzle," sighed Ann.

Finally, Dalia removed the simple wrapping from her present.

"Hmm. I'm not sure quite what to make of this," she mused.

"Nevertheless guys," she continued in a philosophical tone, "how about we give these presents a try; I'm sure our Aunt put some thought into these. She wouldn't have just sent us random junk, right?"

Somewhat later, the children were showing off their creations to each-other. Even Bob admitted that his kit wasn't as boring as he'd feared.

"So, now what?" Asked Cliff.

"Yeah," growled Bob. "That blew. I wanna do something fun."

"Yeah," agreed Cliff. "Like a sightseeing tour."

"Yeah," said Bob. "Like that."

"Me too," Emily half-whispered, "that sounds marvelous."

"But guys," said Dalia, "we're plumb flat broke. And the tour costs 200 units! We can't afford anything like that."

"Well," said Ann, "looking at our presents gives me an idea."

This left Mike (and his girlfriend, who had arrived downstairs after showering) the task of opening the five presents, examining their contents, and figuring out what Ann's idea was.

Ann's present was a diorama kit consisting of five printed sheets of paper.

Bob's present was a kit consisting of six pieces of red yarn, one loop of green yarn, a coat hanger bent into a circle and instructions.

Cliff's present consisted of two jars of white powder and a recipe.

To my great disappointment, the solvers got this one without actually baking the cookies.

Emily's present was a broken jumble of toothpicks:

broken toothpick structure

This was the puzzle that pained me the most to make, as I had to build a beautiful toothpick structure, then mercilessly destroy it.

Dalia's present was a set of eight cubes (1, 2, 3, 4, 5, 6, 7, and 8) and an enciphered note.

This note contains an error; only the lower case letters are ciphered. This was a mistake on my part, but the solvers managed to notice and work around it.

Once our intrepid solvers figured out that Ann wanted to go to a gambling establishment, the story proceeded:

When the children got to the casino, they immediately walked up to a table.

"Why hello, children," said the dealer, "what brings you here?"

"We want to go on a sightseeing tour," explained Dalia, "but we don't have the money."

"We're going to raise it through gambling!" Chimed in Bobby, excitedly.

"Well, children," explained the dealer, "to gamble one requires two things: a stake, and a game."

"Let's start off with the game. What would you like to play?"

"Blackjack," said Cliff.

"No! Draw poker," interrupted Bobby.

Dalia whacked Bobby on the back of the head, "no, dummy, Baccarat. That's a game for kings!"

"What about Crazy Eights?" Said Emily in her small voice. "I like Crazy Eights."

Ann said nothing.

"Those are good suggestions," said the dealer, "but I'm afraid we don't have those games here. Please, enjoy this complimentary juice and iced cubes cocktail while you consider what else you might enjoy."

The dealer reached under his table and set before them a cocktail and an oddly printed napkin.

The cocktail was grape juice with laser-cut acrylic instead of ice cubes (in the shapes shown on the napkin).

Once Mike had drained the grape juice, he was left with 18 acrylic pieces and the notion that they should be assembled into three cubes. After about three hours, I provided a napkin printed in color, which reveals which pieces belong to which cubes.

This turned out to be my favorite puzzle (as well as being this year's "puzzle that is too hard"). The cubes themselves sat around for my entire visit home, falling apart and being re-solved by various family members. There's definitely room to succeed here through brute force, but after getting used to thinking in cubes, one can do quite well by using reasoning to eliminate large parts of the combination space. That said, I haven't had any luck solving from a complete mixed pile.

After finishing the cocktail, Ann spoke up: "High Card Pays Double."

"Very good choice, miss," said the dealer. "Such a simple game -- the name really says it all."

"Of course, you still require an initial stake. You will need a minimum deposit of twenty units to play."

"How are we gonna get that?" Queried Bobby.

"Actually," said the dealer, "I happen to know some folks who could use a little help. Let me give you their information."

With that, he wrote out directions of two businesses -- a gallery and a ballistics investigation firm.

Let's go visit them; which one would you like to go to first?

Mike chose the gallery.

At the gallery:

The children arrived at the gallery and were greeted by the owner immediately.

"Well," said the woman, "there are seven light bulbs around the place that that have burnt out, and it's really making the place look shabby. If you could replace them, I'd pay you 5 units."

"Also, I'm looking for some new pixel-art to hang on the wall -- I'd pay up to 5 units for that as well. But why don't you change the light bulbs first?"

The owner handed the children two boxes of bulbs and set them off on their first task.

Can you find and replace the seven burnt-out bulbs? And perhaps come up with some new art?

And so Mike set off to find all the burnt out bulbs in our ancestral home:

reaching for a bulb

It's no wonder they weren't lighting up properly -- the bulbs were hollowed out, and inside each bulb was a scrap of paper:

the bulbs

After examining the scraps, the solvers were able to create the same pixel art that earned the children in the framing story 10 units.

Then Mike headed off to the ballistics investigation firm.

At the ballistics investigation firm:

"Well, hello children", said the owner once the children had introduced themselves, "I do happen to have some work for you"

"I'm investigating an odd situation in legotownville."

"Someone set off a time bomb, freezing everyone in place."

"I think it was one of these eight suspects, but I'm not sure which one."

"An anonymous tip says that there are clues in three boxes scattered through the town."

"Unfortunately, the are is still filled with residual temporal radiation, so we need to send in a robot. If you can build a robot to retrieve the clues, and figure out which suspect is at fault, I'll pay you 10 units."

"Here's the box of parts; the robot will need to start and return to this landing area with each clue."

Can you make a robot that works as well as the children's did?

This puzzle was a building and control challenge using an old Mindstorms set that's been around the family house for years (neither of us took the LEGOs off to college with us). Part of the challenge is that there was only one motor and the course required complicated navigation.

Here's Mike's remotely-operated vehicle:

Lego vehicle

The boxed clues were straightforward -- pants color, torso color, and facial hair; if I remember properly -- and implicated the LEGO suspect dressed as a red-suited man with a white beard.

Now in possession of 20 units, the children returned to the casino.

"Here you are sir," said Emily, "it's twenty units, just like you said."

"Very good, young miss," replied the dealer, exchanging the unit bills for a stack of chips.

"These are your chips. Each is worth five units. Be careful you don't lose them! And these are zero-unit chips -- you can bet with these to help you learn the game."

"The game, of course, is High Card Pays Double. It's a simple game -- I put four cards out on the table like this," said the dealer, placing four cards face down on the table, "and you put chips on one or more of them."

"Then, I flip them over, and the high card pays double." The dealer was as good as his word, flipping the cards and doubling the bet on the high card, while removing the bets on the other cards.

"That's all there is to it?" Said Cliff, shoving his way to the table. "I can play that."

"Wait," said Dalia, "perhaps we'd better use these zero-unit chips to get a feel for things. After all, it's a long way from 20 units to 200 units!"

The children settled in for a long session of gambling.

Why don't you try your luck? We'll continue the story once you have 200 units.

The key to this puzzle was that the deck was marked. Once the solvers learned this and figured out the marking scheme, they were able to place good bets and make the 200 units quickly.

"Well," remarked Ann, "that does it. 200 units."

"Yay," said Emily, looking down, "let's go on a tour."

"Yeah," said Bob.

"Yeah, yeah," said Cliff, not to be outdone.

"I know just the place," said Dalia, "and they're close too!"

And so the children set off to the tour office.


The agent greeted them as they stepped in the door. "Welcome sirs and madames. Welcome to the best tour office this side of the lake. We have all sorts of tours -- walking tours, bicycle tours, self-guided tours, professionally-guided tours; all sorts of tours. What can I interest you in?"

"Well," spoke up Dalia, "We've been gambling, and..."

"Very well, very well," broke in the agent, "Might I then suggest our most expensive tour? It's 200 units -- well within the means of gamblers such as yourself."

"Sure," said Dalia, "I guess so."

As they embarked upon the tour, Ann, very reasonably, reminded them, "I'm sure this tour will be great, but let's not forget there's yet more day ahead; let's consider what activity to do next while we examine the sights."

Let's go on the same tour the children did; we'll continue the story once you've figured out what next activity the children got up to.

This was another live-action puzzle. The tour guide pointed out things like "couches", "headlights", "edible stuff", "spinach", "spaghetti", ...

"Well, friends," intoned Ann, "all things must come to an end. What shall we do now?"

Almost in unison, the children all intoned: "Chess!"

They rushed around frantically, looking for the chess board. When they finally found it, however, something wasn't quite right.

an odd chess board

"Aren't chess boards supposed to be 8x8?" Asked Cliff.

"Yes," said Ann, "and someone appears to have been writing on this one as well."

Bob looked a bit crestfallen, "well, guys, I needed something to do my spelling grid test on, and this was the only thing that was handy. I was going to buy a new one, really."

Dalia was struck by an idea, "that's okay! Let's play instead with the power of our imaginations."

"Let's pretend that these are the delegates of two warring countries, and this is a negotiating room."

"Here, I'll start. First, of course, the white faction sends a knight to the negotation room to make sure everything is clear."

Ann placed a white knight on the 'a' in 'algae'.

"Okay, so black definitely needs to send a knight as well; and to keep it fair, let's make it so all black's and white's delegates are symmetric," said Cliff, getting into it and placing a black knight on the 'c' in 'scare'.

"Right, so now that the coast is clear, the white king shows up," said Dalia, placing the white king on the 'n' in 'dozen'.

"And the black king goes here, to keep it rotationally symmetric," said Cliff quickly, slamming the black king onto the 't' in 'torso'. And so the children continued, until all the courts of both nations where peacefully on the board.

We'll continue the story after you discover how they managed it.

The remaining pieces to be placed by both sides: a rook, two bishops, a queen, and another knight.

To be clear, the point of this puzzle was to alternately place pieces from each side in a rotationally symmetric way such that each place is was neither under threat or attacking a piece of the opposite color when placed. This is a fun class of arrangements to think about. I recall that I was working on a proof that any symmetric safe arrangement has a symmetric safe construction. I don't recall if I ever figured it out or found a counterexample. If you manage to, please let me know.

With peace negotiated between the warring nations, the children were again in need of a new game.

"We should look under the board," said Emily.

"Sounds reasonable," said Ann, lifting the board. "Hey, there's a photo here."

"Let's figure out where it was taken!"

Why don't your figure it out as well?

This was a long run-around featuring pictures of various bits of bric-a-brac to which was attached yet more pictures. Here's a picture I didn't use:

Elsie the cat

(She's a somewhat sedentary cat, but not that sedentary.)

Exhausted, the children arrived in the solarium.

"Well, that's the last once," said Bob.

"I'm tired of this game anyway," said Cliff, "I want to do something else."

The children pondered what to do next until Bob noticed something.

I'll continue the story once you tell me what Bob noticed.

The final picture in the run-around led to a map of our house, which -- conveniently -- is well-approximated by a 2x3 grid. And if you've been doing puzzle hunt stuff for any length of time you probably understand that that means that the photo locations were pips in a braille message.

For this next bit of narration, it helps to know that the room where the children in the framing story are standing has large windows that overlook the wooded valley behind our house, and -- at this point in the hunt -- it was a dark and cold Michigan winter night.

As they stared out into the crisp air, Bob suddenly cried out:

"Fireflies! Look, there!"

"And there!" exclaimed Cliff.

"Oh, and over there," gushed Dalia, "oh this is too perfect; let's go collect them."

Emily had been watching quietly this whole time and said, "I count ten of them; let's make sure to catch them all."

And so the children donned their outside garments and headed for the flashes of light they'd see earlier.

Why don't you collect the fireflies, then we'll continue the story.

One romp through the woods later, Mike was in possession of ten zip-lock bags containing clocks outfitted with flashing LEDs, fixed-in-place hands, and two letters written on the back of each.


I don't have my notes available to exactly reconstruct this puzzle for internet viewing; suffice to say that the letters on the backs of the clocks formed a linked-list and spelled out instructions for adding time. Once that time was added, the clocks could be read as semaphore, yielding "sleepytime."

The LED flashers were made from the circuit in the clock movement that is responsible for moving the second hand. This turns out to be a cheap way of building a reasonably accurate timebase, especially if clocks are on sale for $2 each and you have a $5-off coupon. In my original vision for this puzzle, the LEDs were to remain in-sync enough that the clocks could be put in order by the flashing. Alas, cheap clocks are not so forgiving (especially with temperature variation).

Three or four of these clocks were somewhat high up in trees. During one installation, I fell a fair distance after the branch I was standing on snapped, for which I felt a bit silly and a bit bruised.

When the children finally arrived back inside with jars of fireflies, they were all very tired. It had been an exhausting and fun-filled day.

"Gosh," Bob mused, "what a day. So full of adventure. Do you suppose this is what our Aunt intended when she gave us those presents?"

"I'm not sure," ventured Emily, "but I'm glad."

"Yeah," said Cliff, "double-yeah."

And with that, the children all went to bed.