The Highlight Reel

This is part 10 of a 10-part series.

We’re finally here. Although I had to delay until after Ditch Day 2014 to finish this series because I stupidly left my desktop in a state that didn’t let me retrieve all the videos I needed, it’s finally done. Before I get to the highlight reel, I wanted to thank all of the people that helped make my stack possible:

  • My co-stackers.
  • All of the alums who helped out with our stack.
  • All of the Caltech personnel that let us use various spaces and things they were responsible for.
  • Everyone who went on the stack!

I’d go into specifics, but I’m sure I’d miss someone.

The highlight reel is mostly video footage I’ve posted elsewhere in this series with a little bit of extra footage that didn’t really fit anywhere on its own. I hope it provides a good summary of the day and memory store for everyone who was involved ūüôā It’s…kind of long.

Now that I’m done with the Ditch Day series, I guess I’ll need to find new things to write about! Hopefully, I’ll be able to¬†write a few essays touching on software engineering, music, e-sports, or other interests that I have. If there’s any interest, I might write another post with advice for next year’s seniors from someone who has now been on both the senior and alum side of things. For the next little bit, I’ll probably focus on my next reading project, though, as I’ve been devoting all of my time to writing the blog and have let some other projects slip.

As far as Ditch Day, I enjoyed helping out where I could when I came back this year and am looking forward to doing so again next year. In a broader sense, I think life would be a lot more exciting if we made activities as elaborate as these just so that people could have fun with them. Maybe I should look into trying to make that happen out in the real world.


As a sort of below the fold shameless plug: I’m doing a bike ride this fall to help raise funds for a charity that supports MS research. Please consider giving a tax-deductible contribution here¬†and check out both my and my team’s progress here.

The Grand Finale

This is part 9 of a 10-part series.

As I¬†mentioned at the end of part 5, the Space Alert puzzle led directly into the grand finale. As soon as the frosh completed the puzzle, an alarm sounded and the giant crane in that space began rising, revealing the supercomputing core in a container made of mylar. The core itself was made out of a glass bottle filled with some flammable liquid (alcohol? acetone? I can’t remember).

Just as the group removed the core from its location, two alums (Daniel and Ryan) appeared on a catwalk above them, and yelled “What are you doing? Stop!” At that point, Kurt yelled “run!” and took the group through a back room in the building. The room was already filled with vaguely science-looking things (it being a physics lab and all), but we arranged them to force the group to take a somewhat circuitous path around the room. We also added a few extra touches: a spinning red siren light (like this one), a blacklight, and a semi-transparent plastic sheet that we turned into a wall and¬†on which we painted the Vector logo in a paint that would glow¬†under blacklight. When they left that room, the group had to go through a circular tunnel and climb up a set of stairs that took them to a familiar location outside, through a door they likely never even noticed.

We actually didn’t know about the existence of this room or the tunnel when we asked for the space in which we were building the Space Alert puzzle. One day, Matt came to Jeff and me and said “you guys have to see this.” We walked to the area and Matt took us to the back room. As we saw the room, and especially the tunnel with its exit, our minds were fairly blown. We knew we had to use it, but didn’t have any good ideas for how to use it until we realized that¬†the beginning of our grand finale could be an awesome chase scene.

When the frosh finally made their way to Blacker courtyard, they found a small “furnace” in the middle. This was where they disposed of the supercomputing core, a la Portal. The frosh got their final message on the AI and the day concluded.

I had to take some video of the escape tunnel myself, since they were too busy running to record.

The next post will be the last! I will be posting the highlight reel of all the video footage I have.


Behind the Scenes: Stack Design, Build and Test Process, Cold Hard Cash and the Day of

This is part 8 of a 10-part series.

Before I talk about the finale and make the video highlight reel, I want to tell a few stories about the planning, building, testing, and deploying of the stack. I wish I could tell you about all of the little experiences I had while doing so, but that would make an already long post even longer, so I’ll try to tell the most relevant pieces.

Stack Design

The stack design all began on the night before a fake stack sometime second term. We were out getting some delicious late night LA food after having finished our fake, and on the way there we confirmed that the three of us were working together. I proposed that our stack theme should be an original content time travel stack, and I think we all pretty much agreed at that point, since nobody had a strong opinion on something else they wanted. I had actually discussed how cool it would be to have a time travel-based stack with Matt a few years beforehand, so I was glad that the idea was getting implemented.

Then, we discussed how we wanted our stack to be flavored. Time travel could imply visiting historical events, or it could be a science fiction stack like ours. We chose the latter because we felt it would be more compelling to our target audience, as well as because it’d be kind of annoying to have to research historical events¬†in addition to¬†coming up with a good plot. Once we decided on a more sci-fi flavor, one of us (probably Matt) came up with the idea that it should be set at Caltech in the future. It seems like it might be a cheap cop-out, but I think it served to help the immersion without losing much.

Our remaining¬†design challenges fell into two categories: plot and stack elements, the former¬†being somewhat uncharted territory for us and people we knew. We spent months making regular trips to my room to have a “nice refreshing soda” (after our on-campus convenience store runs), where¬†we sat in front of a Google doc that went from being a bullet-pointed list of things we needed to do to just a disorganized mind dump of stuff. Somehow this never really became a problem; I guess ctrl+f is a powerful thing.

I don’t remember much about how the plot developed. I think it sort of organically grew as the three of us contributed ideas. Matt is a pretty gifted story-maker, so his contribution was definitely quite valuable. Much of our time was spent debating details of our story and whether they were internally consistent.

For the stack elements, we had already developed some ideas for our bigger mainstays while we were underclassmen¬†(definitely we came into the design process of the stack already having the preliminary ideas for what later became the mirror maze and the Space Alert puzzle). For the rest, we wanted to balance puzzles with activities (and, where possible, combine the two), as well as including¬†at least one brute force element¬†just for tradition’s sake. That’s how the minor puzzles came about: we just ran with some of our one-off ideas to balance out the stack and fill out the day.¬†We did actually wind up having to cut one of the puzzles that we developed, which would have involved something to do with pinballs rolling around in multi-layered mazes that you controlled by tilting the entire structure.

The horrible mess of cables that threatened to take over my room entirely during the build process.

The horrible mess of cables that threatened to take over my room entirely during the build process.

When we actually got around to writing the detailed parts of our stack, including timings, we had to follow the advice given to everyone, which is that frosh are kind of dumb. A more charitable way to put that might be that it is difficult to gauge the difficulty of puzzles, even with play-testing by alums, when they’re developed in secret. The stack that I went on my frosh year created a slight workaround for this problem¬†(I don’t know if they got it from anywhere). They made their puzzles a little bit on the hard side and included several envelopes with each puzzle with notes that said “open if still working at [time],” each of which offered successively more explicit hints, the last of which offered the answer to the puzzle. The reason they were made to be harder is that having a stack go too fast is pretty poor as well, as they need to be stalled with other puzzles (sometimes “best-of” puzzles from other stacks that are resettable) to fill out their day. We used this idea, albeit digitally, and it seemed to work out pretty well: our stack was actually almost exactly on time for¬†at least half of the day.

Build and Test

A large part of building our stack was making sure that other people¬†would be able to actually solve any of the puzzles, even if we did tweak the difficulty up. After all, much of engineering is about coming up with an idea and then iterating. Our progression was mostly to try it ourselves, then test it with each other, as much as possible, and finally test it with a group of alums. Sometimes a lot of changes happened during testing: the mirror maze got a few tweaks to difficulty and correctness with alum play-testing (I had a bug where holding down a button would cause the input to freeze for a while as the buffer cleared, so I put out instructions not to hold down buttons), the Skype puzzle developed from Matt’s original form to its final form over the course of a run-through or two with Jeff and me and later some other seniors, and the wire puzzle was completely redesigned when alum play-testing showed that its original form was kind of crap. It’s interesting to think back to this process, because it almost feels like we were doing UX design (certainly not something I’m good at), as we were testing how people would interface with our puzzles, and what was confusing or unsatisfying about the experience.

I felt like lord of the monitors when I still had the mirror maze controlling computer in my room.

I felt like lord of the monitors when I still had the mirror maze controlling computer in my room.

Of course, sometimes testing it had to sort of wait until the last moment.¬†The only people around on campus who can test your puzzles are other seniors, and they’re often busy with their own stacks. The alums are very useful for this, but they only show up for the week before. That’s why much of the week before our stack was spent testing (thankfully we had the puzzles built in time). I would definitely advise any seniors reading this to build their stacks in time for alums to be able to run through it at least once. In addition to lack of QA manpower, many of our stack components were built in our rooms and couldn’t be moved on-site until the night before (since we didn’t have access to the spaces until then). Thus, we were forced to do some creative limited testing in our rooms. At least we were seniors, so we had the bigger rooms!


Ditch Day stacks are almost entirely self-funded, and ours was not cheap. Looking at our budget, it looks like we spent about $1900 total on the stack. The biggest expenditures were the $600-800 on the mirror maze (we spent $370 on mylar and about $185 for arcade buttons and controllers, though some of both were also used on the Space Alert Puzzle) and the ~$400 we spent on our shirts from CustomInk (for a total of 18 shirts: 12 for the stackers, 3 for us, and 3 for alums who helped a lot). As I’ve mentioned before, the tablet was only $55, which was awesome.

Some entries in our budget include “Ilya likes scotch” (Scotch Tape), “My(b|l)ar Part 2” (our second purchase of mylar — I think this was a reference to the Electric Six song “Gay bar Part Two” somehow), and “2800 feet of 32 gauge mag wire” (that one’s exactly what it sounds like). While dealing with the mylar, we often called it the “mylarium invectus domine”, mostly because we were sleep deprived and thought it sounded funny. The fact that the final code to the mirror maze was “MID715” was a callback to this that only we understood.

Fortunately for us, we managed to get a little bit of help with the money side of things. First of all, Blacker Hovse subsidized some of the cost of Ditch Day stacks, depending on how many spots were on the¬†stack. The amount of the subsidy that my stack received was about $400. Furthermore, at the end of the year, the seniors hold a “garage sale”, in which they try to pawn their (sometimes useless) Ditch Day leftovers on the underclassmen.¬†My stack managed to sell off about $420 worth of stuff this way. Thus, at the end of the day, we wound up spending about $1500 on the stack, which was “only” about $500 per person building the stack.

Overall, it is very much the case that more money does not make for a better stack and vice versa. We spent a lot of money because we were ambitious about the scale of our construction and at least partially because we were kind of lazy about shirts (which we’d still probably have to spend ~$150-200 on if we screened our own). However, other stacks in Blacker barely spent any money at all and received positive reviews. It really depends on your vision for the stack and what kind of flavor you want it to have. I’m grateful that my fellow stackers and I were willing and able to spend so much money!

Stories from the Day of

The day of Ditch Day started off pretty poorly for me, despite an awesome prior week. As I¬†discussed before in part 3, a dumb issue with the Javascript for the app caused me to pull my first true all-nighter at Caltech, when earlier in the week we were speculating that we could actually get quite a bit of sleep that night (and if I remember correctly, my fellow stackers¬†did get four hours or so). In fact, while I had gotten to bang on people’s doors to wake them up for every fake ditch day for which I was a senior, I had to miss doing so on the real day of for this reason.

Fortunately, I managed to get the issue solved before the seniors officially began Ditch Day by leaving¬†for their undisclosed off-campus location (our off-campus alley, Munth), as being a senior on-campus during Ditch Day is fairly perilous. At Munth, I was running on adrenaline (and maybe a little caffeine) for the first while and helicoptering on the inputs that the people on our stack were giving us, as well as updates from alums who were watching our stack. However, after a little bit of time, I started crashing and wanted to take a nap. This was not very much in the cards for me, though, since I was apparently the only person on my stack who actually had alums’ phone numbers ūüė¶

Our stack was quite perfectly timed in the morning. If I remember correctly, they were solving and arriving at puzzles within minutes of our schedule. This was, of course, helped a lot by our ‘clue envelopes’ and the fact that the people on the stack diligently used them when needed (which I don’t think was that often). At lunch, we were quite optimistic about our stack actually working out. There was one exception, which was the fact that our stack thought the mirror maze was broken for some reason when it wasn’t. I think it had to do with their accidentally muting one of the speakers. After lunch, Jeff and I cloak-and-daggered on-campus in the hopes that we could fix it so that our stack could do it at the end of the day (we found nothing broken, by the way). On the way back from that, we almost got duct taped to a tree by some underclassmen, but Jeff’s and my sprinting in flip-flops skills and the underclassmen’s apathy skills won the day.

The afternoon was a completely different story. It started off pretty uneventful, but we were soon getting reports that our stack was skipping elements (maybe the tying up of Kurt, maybe the wire puzzle sabotage, maybe something else?). I tried sending some messages over the tablet app to not skip things but it didn’t seem to be reaching them. More reports seemed to come in to confirm this news. A combination of confusion and sleep deprivation resulted in my getting very angry and frustrated, as I was worried that they were ignoring the plot, which was a pretty major component of the stack. I worried that this meant they would have hated the experience because of that. Other alums and seniors were trying to calm me down while I tried to take some deep breaths and¬†see where the frosh wound up. It was overall a very stressful hour or so — it isn’t a fun feeling worrying that months of effort had gotten wasted.

In the end, it turned out that the frosh had just decided to split up to do the sabotage portion of the stack and completed it quite a bit sooner than expected, which was the cause of our faulty intelligence. Thus, it wasn’t the case that they missed fairly significant chunks of the plot. I calmed down quite a bit after hearing the corrected news, although apparently the news that I was very unhappy filtered through to the frosh when they decided to prank our rooms after getting done, so they skipped mine. I feel sort of bad for that.

When Ditch Day was over, we got to see the people who went on our stack and talk to them. That is when I found out that they had mostly positive things to say about the stack, which made me quite happy. I even had a junior tell me that it was the best stack he had been on. Thankfully, I got to end the day feeling that my stackmates and I had done a very good job, and we had a few days before our required clean-up to run our biggest puzzles for more people in the house!

Other Misc Stuff: Non-Newtonian Fluid, Kidnappings, T-Shirts and Time Machines

This is part 7 of a 10-part series.

This time, I’ll cover a couple more minor things that I couldn’t¬†find a place to put.

Non-Newtonian Fluid Puzzle

The frosh were sent to Blacker Beach, where the AI informed them that it found 20 acrylic chips containing the next code in the mysterious goo they saw there. The acrylic chips were small circular pieces of acrylic that had a letter and a number laser cut into them (I think it was Brad who did the laser cutting).

The goo was a mix of corn starch and water (by the way, carrying several 50lb bags of corn starch is pretty fun). In case you didn’t know, the result of this mixture is an awesome fluid, called a Non-Newtonian fluid,¬†whose viscosity is dependent on how quickly you try to move through it (technically “shear rate”). You can get up to some pretty crazy shenanigans with it. This property made it ideal for making the frosh search for small objects inside it (it’s especially fun for people who haven’t gotten a chance to play around with this sort of thing).

Since this was obviously a very messy process, we had to do the mixing the night before. We laid down a simple support structure, four 4x4s in a square with some plastic on top, and added a bunch of our two ingredients. Then we began stirring and added more of either substance until the overall compound was well-mixed and the consistency was what we wanted.

Late night mixing

Late night mixing. Also my wonderful Ditch Day beard.

It was as much fun to do the mixing as it is to play with it, since the mixing basically just involved playing with it. We also asked some alums to come by during the day and mix it a little bit, since the goo would have settled during the day.

Once the frosh found the code, the AI opened with,¬†“Well shit, I suppose I should have expected it was going to be here.¬†Who would have thought that a collaboration between Vector and the Caltech physics department would have labs in a physics building?” It then instructs them that they must go ahead and complete all the sabotages that happened to them, including kidnapping Kurt, before they move on to the Physics building to complete their final mission.


For the consistency of the timeline, and “so that Kurt will reveal important exposition to past you,” as the AI put it, the frosh needed to go to an early part of the day: before they first found Kurt tied up, but after they gave the flash drive to him in the SAC. Once they found Kurt, they needed to make sure to steal the drive from Kurt as well as tying him up in the back room where they found him. As we said in our announcements, “there is no paradox, only self-consistency.” For this, Kurt needed to be standing around in Karman, acting unsuspecting. One hard part was that only a little bit later (in about half an hour), Kurt needed to be by the physics buildings to help the group¬†do the final puzzle.

Enter enlisting more alum help (in this case, Aria).¬†She had to come in right after the frosh kidnapped him to rescue him, in addition to being the one to first tie him up earlier, but hopefully not be seen by the frosh. We also made sure to warn both Aria and the frosh not to cut off Kurt’s circulation in their earnestness. Aria’s tasks with this fit into a larger master schedule that was in a Google Doc that we had and wound up generating a lot of e-mails and supporting documents sent to alum helpers.

From Kurt’s perspective, this was also potentially quite challenging. At 1:15pm (lab time), Kurt was acting surprised that the group was untying them since they had just tied him up. At about 2:45pm, he was standing around in a hallway and surprised that he was being kidnapped and tied up. At 3:30pm, he was again on their side and had to be helping them destroy the quantum super-computing core. We engineered it this way because we thought the stark contrast would stand out to the frosh and make the experience feel more authentic.


I’m particularly proud of our T-Shirt design. Somewhere in the middle of putting together the stack, we¬†began to think about our T-Shirts and our posters, so we began searching for cool illustrations of wormholes. We found two that we really enjoyed, and couldn’t decide which one we liked better, so we made one the T-Shirt design and one the poster design (with thanks to Darcy for designing the poster).


The t-Shirt front design

I actually spent a few hours learning how to use the pen tool in Photoshop so that I could draw that curve. Matt and Jeff watched me draw it and we all made sure that we were getting it just right. The idea was to visually depict the concept of traveling through a wormhole, as well as to depict a vector, since that was our stack’s and fictional company’s name.

We also spent a while trying to come up with the font to use, checking pretty much every font that I had on my system. We wanted something that was a good mix of professional and sci-fi-like. We wound up settling on the Starcraft font, whose name I don’t know: all of the fonts I can find online merely refer to it as the “Starcraft font”.¬†It was a bit hard for us to make the choice, since it sounds very silly to use the Starcraft font, but we decided that it looked very good and most people wouldn’t notice the association.

Most people at Caltech use the on-campus silk-screening house to make their T-Shirts. Having done it once for one of my fake stacks, I decided “never again.” It’s pretty fun, but quite time-consuming and difficult to make look good. Furthermore, the design we picked wasn’t exactly the easiest to print, as you can probably tell if you’ve ever done silk screening before. Fortunately, we found Customink, which I can whole-heartedly recommend. They have designers who will re-draw your design so that it’ll actually work as a silk-screen (which usually involves mixing it down to 2 or 3 colors and making sure there aren’t any very small lines that’ll get ruined in the process). The only downside is that the shirts wind up being fairly pricy unless you get a very large number of them (I think we ordered about 20 and it was about $25 a shirt), but it was totally worth it.

The t-shirt back design

The t-shirt back design

Time Machines

I honestly don’t remember what I originally had in mind for this section when I was naming this post, so I’ll instead share a few vaguely related stories about planning the stack, ahead of the next post. Our original plan for making the group time travel was to have a location (or several) that they could go to that we could designate a “time machine”. Unfortunately, this proved unfeasible for a few reasons. First of all, it would create a lot of extra work. We envisioned something like a room that would be filled by a smoke generator, with strobe lights flashing, and a bunch of clocks on the walls that would suddenly start rotating quickly (or at least something equally sci-fi-like). We wound up settling on making a webpage¬†that fulfilled the clock portion somewhat and putting it up on all the computers in UGCS. Second of all, the idea of making the group walk all the way back to the same or same few locations seemed somewhat tedious and un-fun. Finally, we already felt like we were running short on time with our stack, so we decided that we would just have the tablet “jump” them for certain events without their moving much, and have a “current time” and “lab time” display there. Perhaps it was a little bit less immersive, but definitely more doable!

Speaking of time planning, Matt did a lot of delicate planning for when each puzzle ought to start and end. Matt made the Google Doc with the master schedule I mentioned earlier, and it had all the puzzles and activities timed out to within 15-30 minutes, along with all the things that needed to happen at all of those times and what the “current time” was within the plot at each of those times. Our morning timings actually wound up being pretty spot on, although lunch would have provided a good sync point in case we weren’t. Our afternoon timings were a bit less correct (though fortunately not fatally), but I’ll talk about that in the next post. I’ll also discuss what we did to make sure the timings stayed more or less on, as well as some other planning and day of stories.

Misc Puzzles: Fan Puzzle, Skype Puzzle, and Wire Puzzle

This is part 6 of a 10-part series.

Last time, I covered the second of our two largest undertakings as far as puzzles on my stack. This time, I’ll cover three of our less complex puzzles.

But first, an update! I finally got a hold of a video of our dinner announcements from the night before Ditch Day, so I put that video up back on¬†part 2. It contains my stack’s announcements plus a few more that I added just because I felt like they helped give a good example of what announcements are like in Blacker.

Fan Puzzle

The frosh learn that the access codes to¬†various Vector time machines were changed without authorization and that Vector believes their stacking senior potentially left the codes in a puzzle that had to be abandoned. They proceeded to the North end of the old Y building and walked in to discover a well-lit area with three rooms, each of which contained a box fan. Each fan was numbered and had one side’s cover taken off. Otherwise, not much else was apparent about the fan.

But wait! One of the rooms had a strobe light in it and the lights off. Bringing the strobe light and the fan together allowed them to freeze the fan blades in place. They found that there were weird symbols on each of the fan blades. Somewhere else in the area (which contained about four rooms), there was a key which correlated color and shape to a letter, as well as a pictorial description of what order to read the blades in.

Best song to play when strobe lights are playing. Also, this blog post best read while listening to this song.

Since every good Ditch Day stack ought to have a brute force component, we hid two more strobe lights behind a closed and locked door and left a sledgehammer suggestively placed next to the door with a note that said “Note to self: Make sure to leave sledgehammers for brute force component” on the door. Since this was supposed to be part of the disappeared stacking Senior’s stack, this sort of fit into the theme of exploring the unfinished portions of a stack.

It was okay to destroy the door since the Old Y building was theoretically slated for demolition. There were two unfortunate realities of this part, though. First of all, they didn’t have to destroy the door because it just opened with a kick. Moreover, the additional strobe lights didn’t wind up being needed: we originally designed the puzzle with colored symbols on the fan blades and put colored filters on the strobe lights, hoping that only one color would be¬†legible¬†with each light. Sadly, all the symbols were visible with all the lights, so the puzzle wound up being a bit easier than expected.

One of the fans

One of the fans. Photo courtesy of Moya Chen.

The final password wound up being ‘941fjmbew3pgkd526isclzqyah7v8t’ . An advantage of using the tablet was that we could make the passwords random strings and prevent meta-gaming the answer (oh, we have “B_ckman”. The answer must be Beckman!) but the downside was that there wasn’t really any sort of error-checking built-in. During the course of the puzzle, the group read “iscl” as “i5cl” (partially because I hand-wrote the key, oops!) and we had to send them some real-time messages over the tablet to correct them. I think I had to actually make the messages make some noises in order to get them to notice.

I believe the idea for this puzzle was Jeff’s and I think we came up with it in the stage where we were trying to add some more minor puzzles to fill out both the plot and the number of activities. I would say this puzzle had one of the best effort-to-fun ratios on our stack. Here’s what the frosh captured:

Word of caution: Lots of strobe / flashy light footage. Don’t watch if that’ll make you sad.

Skype Puzzle

This one is one of my favorite parts of the stack. The frosh were sent to Beckman Institute to access confidential Vector files, which anyone in the Caltech community is allowed to view, but nobody is allowed to bring out of the building. Furthermore, the decryption process would take a while, so the two groups were ordered to split into two different rooms.

In designing this activity, I started with the idea that I wanted a puzzle that forced the stack into two groups in separate rooms connected by a Skype call. I went through a few ideas, including having two rooms each with five computers and having each member of the stack doing something on each of the interacting terminals (would have been really cool), or having some sort of big electronic display in both rooms that the frosh would have to interact with. This is ¬†one of the few ideas I had that I was forced to mentally scale back, since it was getting pretty unrealistic and we were already taking on two major projects. The tricky part was coming up with a puzzle where the groups would have asymmetric information but couldn’t just easily relay the entire puzzle to one room and have that room solve it. I’m not convinced we 100% hit that goal, but it still turned out pretty well.

The fundamental idea for how the puzzle turned out¬†came from Matt. His inspiration was from some subfield of Physics (can’t remember which) and dual latices. One group was given a circle¬†with three annuli¬†cut into wedges¬†that had binary values in some of them. The other group was given a grid with binary values in some of the squares. The number of wedges in each annulus of the circle was equal to the number of vertices in the corresponding ring (out from the vertices surrounding the center square) of the grid. The frosh needed to figure out this correspondence, figure out that the value in a grid space was equal to the Z2 sum of the vertices surrounding it, communicate the values across the call (we told them no video — sending video over a temporal link is expensive!), and find the vertices that are unambiguously determined to get the clue.

Matt’s original idea involved two dual grids, but at some point during play-testing we decided to change one of them to rings. I think it was in order to hint more strongly at the correspondence.

One of the groups at work. Forgive the crappy quality -- I had to take a screenshot of the video. The green is what was provided, the rest was what the group drew.

One of the groups at work. Forgive the crappy quality — I had to take a screenshot of the video. The green is what was provided, the rest was what the group drew.

The puzzle was presented on a whiteboard with acrylic glass attached to the front. The unchanging parts of the puzzle were on the whiteboard itself, and the glass prevented erasing of those parts. The glass allowed them to write guesses and other information on top without screwing with the puzzle itself. We decided to do it this way mostly because it looked nicer than just using a whiteboard and permanent markers and partly because we had the time to do so!

One of the nice parts of having the puzzle occur over Skype is that we got to listen in from our undisclosed off-campus location. It was pretty amusing (and frustrating!) to listen to them work through the puzzle. My favorite part was when they began just reading off portions of the puzzle and it sounded like some weird code, as they were just reading off 0s and 1s!

Afterwards, they got access to¬†a flash drive and some string and told to get it out of the building. However, they couldn’t take it through the front door, as there were guards blocking the way to the front entrance (thanks Kevin and Isaac for doing an amazing job — even asking to check the group’s student IDs). Thus, they had to get to the roof and smuggle it down to the ground somehow.

Of course, the obligatory video:

It took them a while to solve it but the video was already getting long, so I cut out the boring middle part ūüėõ

For this puzzle, I want to give a shout-out to the person in charge of allowing people to use rooms in BI. He gave us full access to the room starting the night before, including giving us keys to the room for no other reason than that we wanted it for a stack. Yet another example of the honor code at work!

Wire Puzzle

The frosh, having recently completed their hand-off of the valuable flash drive that they smuggled out of Beckman to a Vector agent (Kurt), are told that they must proceed to SAC 15 to make their next jump in time. However, when they enter the room, they find that the “high conductance nylon” (translation: string, because we were a bit too budget constrained to use real wire for this puzzle) wiring in the location has been sabotaged! They had to re-wire the room before they could make their next jump.

To be honest, this one puzzle is the reason I’ve been putting off this post for so long. I think the initial form of this puzzle was Jeff’s idea and was executed by him, and the final form of the puzzle was created by Suzanne (Jeff’s girlfriend / Blacker alum) after some play-testing. The general idea was to have a puzzle that was difficult to do because completing it involved creating obstacles for yourself around the room.

[ I’ve asked Jeff and/or Suzanne to help me out by writing out a short blurb on this puzzle, but they’re both pretty busy and I already feel bad for bugging them as much as I have, so I promise to update this post when they get back to me. Hopefully that should be by next week! ]

The video didn’t really demonstrate too much of the puzzle — I’ll leave it for the big compilation at the end!

Next Time

Next time, which should hopefully be sooner than five months from now (given my goal of completing this series before the next Ditch Day, which is Tomorrow of course), I’ll discuss some more of the smaller components of our stack, including starting into some of our logistical issues. I’ll also have some fun trying to decipher what I meant when I originally wrote the title for that post.

The “Space Alert” Puzzle

This is part 5 of a 10-part series.

Oh dear. I seem to have accidentally stopped blogging for three months. Thus, I feel the need to begin this post with some (bad) excuses:

  • Since the last time I posted, I have gone through interviews with a bunch of companies and now have a full-time job at Palantir!
  • The subject of this post is on a puzzle I wasn’t too involved in and therefore have been putting off writing about.

Like I said, bad excuses. That being said, you’re probably here to read about my Ditch Day stack, not about why I haven’t provided you with more reading material about my Ditch Day stack.

The Puzzle

It’s time to ramp up for the exciting climax. The frosh are back to the current time and meeting up with Kurt to go retrieve the time travel core in the Syncrotron lab. When they arrive to the lab, they find a large housing stamped with the Vector logo, on which they can climb and walk around. There are many buttons and switches all over the housing (many more than there are frosh).

Kurt explains to the frosh that they have to perform a complicated security override procedure to open the housing containing the core. This procedure is much like a password, and Kurt already has the answer to the puzzle. It’s a sheet that details which buttons are to be pushed down at each time-step (which were about 10 seconds apart) and which position each switch was to be in at each time-step. If anything is wrong when it is checked, the frosh are taken back to the last checkpoint (there were checkpoints after the 3rd and 6th rounds).

Since there were so many switches and buttons, the frosh once again had to determine the most effective strategy to cover each switch. I can say, since I got to experience the puzzle afterwards, that it’s a lot of fun, actually. This puzzle took groups approximately 30-45 minutes to complete.

After completing the puzzle, an alarm sounded, announcing the fact that the security override procedure had completed and that the core was free to be retrieved. This is where the Grand Finale began (to be detailed later–ooh suspense).

Video of the puzzle in action.

Behind the Scenes

The buttons were the same type used for our Mirror Maze. The switches were just handed to us by an alum who was two years older than us and happened to have a bunch of them sitting around (I think because he bought them for his own stack and never used them). The whole puzzle was powered by a Teensy++ 2.0, effectively an Arduino board with more inputs. Jeff had to spend far too many hours soldering the many wires to the board, and it kind of looked like a terrible centipede afterwards. We actually managed to sell off the board for a decent price after Ditch Day based on the fact that the next person wouldn’t have to spend so much time soldering wires to it.¬†The code was written by another alum, Patrick.

The housing was built out of a combination of particle board and dance platforms we borrowed from Blacker.¬†According to Jeff, the housing was made of three 4 ft. and one 8 ft. dance platforms bolted together and a 2 feet x 2 feet area 12 feet in the air. The entire structure was then covered in particle board. Fun fact about the housing: when we were reporting what we were doing to the powers that be (for safety reasons), we told them that our element would be a “box with buttons on it that the stackees would run around.” -shifty eyes- It’s okay, because we made sure the structure was safe anyway.

The folks in charge of the Syncrotron lab definitely deserve a huge shout-out here. Matt talked to the people in the physics department in charge of the lab, which is pretty much a large warehouse-like area on campus where physics experiments that need a lot of space live. That area contains a lot of really expensive equipment too. The Syncrotron people were not only extremely accommodating in giving us a huge area to build the housing for the core, but then also gave us a large side room that we used for the grand finale. Some people working in the lab were also cool with letting us use their crane. I think this situation is a perfect example of the Honor Code at Caltech having gone extremely right.

The Concept

Similarly to how I had been nursing the idea of the speaker puzzle for a while, Jeff and Matt had been discussing the idea of making a puzzle based on the board game Space Alert. In the game, you are given a sound track (on a CD or as an mp3) that tells you events that will happen at particular times (such as alien ships attacking yours). While that soundtrack is playing, you have to choose actions to do around your spaceship. If there is static on the soundtrack, it means communications are down and you cannot discuss what you are doing with your team for that small duration. Often times, you will find that your actions conflict with your teammates’, and thus you are tripping over ladders and not completing all the tasks you need to do and dying horrible deaths.

We liked the idea of having a “puzzle-tivity”, where you had to figure out what to do, but executing the correct answer relied on getting timing correct. We also liked the idea of a puzzle where we “gave out the answers” at the beginning, and people getting mixed up and blocking each other while trying to scramble to do things. This is more or less how this stack element was born.

Misc Notes

It occurs to me that I forgot to mention one thing. As I said in my description of Ditch Day, the seniors are not allowed to be on campus during their stacks. How did we have video of our stack? We gave them a Flip Cam at the beginning of the day (along with the tablet) and told them to record their day. This was an idea stolen from the stack I went on when I was a frosh, and it was a great idea. The result is an amazing video reel of the happenings of the day.

The Mirror Maze

This is part 4 of a 10-part series.

You’re our group of time-travelling frosh, ordered to report to the North end of the old Y building, because Vector Corporation has tracked the saboteur to that location. The Artificial Intelligence tells you that it can sense some strange signatures coming from the building, almost as if there is a time machine active there. You open the door and find that it is pitch black inside. From the little bit of light streaming in through the still-open door, you see signs that instruct you to remove all of your belongings and place them in the “magnetically shielded” (cardboard) box, as there are heavy magnetic fields in the area. You’re also given a very dim, blue keychain flashlight in another box. You have no idea what’s going on.

The door is shut. Now it’s completely dark inside. You notice that there are fake walls set up, made of a thin and reflective material. Your group walks around, trying to figure out what is going on. If your night vision has returned, you might notice some of the buttons around the room. Suddenly, someone in your group gets the bright idea to press one of the buttons. A voice comes on the speakers in the room and says:

“Time machine artificial intelligence online. Time travel protocols initiated. Scanning….Warning! Bombs are being sent from the future to this location. In the event that they are not disarmed, emergency procedures will be engaged to ensure the safety of this facility. Twenty signatures incoming…now!”

Then, all you can hear is a weird series of ticking noises. What’s going on? Then this happens:

That’s an abbreviated video of a typical experience through the mirror maze puzzle. A typical group would take somewhere between 30 and 50 minutes to complete the puzzle/activity, from walking in to finishing. As there isn’t any video of our actual stack going through the puzzle, I took this video during one of the many repeat runs we did during the weekend after Ditch Day (Matt and I liked to joke that we felt like theme park ride operators).

Puzzle Layout

The actual layout of the puzzle was a large maze with mylar walls (we easily bought 10-12 rolls of mylar for this and our other main puzzle). Inside the maze, there were 10 speaker buttons (Ultimarc GoldLeaf pushbuttons¬†next to a computer speaker) and 10 “light-up” buttons (Ultimarc ClassicRGB LED buttons¬†which lit up when they were active). The first button was always a speaker button that was near the door (to ensure that the groups would hear the first one rather than being confused for a long time), and the rest were played in a randomly chosen sequence. Whenever a speaker played the high-pitched “bomb noise” or a light-up button lit up, someone would have to press the associated button within the specified time. Note that there were twenty buttons but only about twelve people, so they had to be fairly efficient in covering the rather large space.

The beginnings of the mirror maze. Note the markings on the ground denoting future maze walls. Those were...mostly followed.

The beginnings of the mirror maze. Note the markings on the ground denoting future maze walls. Those were…mostly followed.

Getting to observe groups solving this was great, because you could actively see learning occur. In some order, the groups had to realize which buttons to press (the ones that were beeping or lighting up), that there was a back room that was hidden by a door screwed into one of the pillars in the room, that there was no set order to the buttons so the group had to manage to cover all of them, and the best strategy to cover all of the buttons. At first, the group would spend its time shouting and trying to figure out the best strategy. By the end, they would work in near complete silence, as you can see in the video.

The door blocking the way into the back area. Most groups took a while to realize this was a door.

The door blocking the way into the back area. Most groups took a while to realize this was a door.

The puzzle grew out of an idea I had been toying around with since I had been a sophomore. One of my favorite puzzles on my frosh year stack was one in which we had to push buttons near speakers that played the Ride of the Valkyries (something that is “forbidden” to play at Caltech except during finals week, and can cause strong reactions from students) to stop them. I wanted to do something similar but somehow top it. My original idea involved having speakers lining a very long hallway and having the frosh chase their own voices down (fitting into the time travel theme). One of Jeff’s ideas for a puzzle was to riff on the scene from Skyfall where James Bond is in a room at the top of a skyscraper with lots of reflective windows, trying to fight a bad guy. You can sort of see how that eventually became the mirror maze.

Gory Details

So, how do you drive this puzzle? Most of the code was actually code from the puzzle on my frosh year stack, generously given to me by Andy Matuschak. Most of the logic was written in Ruby, with the sound part regulated by mplayer (did you know that you can arbitrarily select what channel to run a sound out of in mplayer?). I added in the part that drove the light-up buttons, which were driven by the pacdrive utility connecting to an Ultimarc Pacdrive board. The button input was processed by an Ultimarc I-Pac.

In order to actually be able to plug all of the speakers into the computer, I had to put three 5.1 surround sound cards into it (one that happened to be lying around from my frosh year, and two that I had to buy)!

It's hard to sell off sound cards to people these days.

It’s hard to sell off sound cards to people these days.

For the wiring, we made the decision to cut costs by purchasing magnet wire. Upside: Incredibly cheap, given that our rough estimates for amount of wire required for this activity was about 2400 feet. Downside: Jeff spent many, many hours having to work on the wiring. It turns out that the best way to strip away the enamel insulation on the wires is to burn it off, which is a rather painstaking process.

Only kind of a burn hazard.

Only kind of a burn hazard.

Also, the building we used for the mirror maze puzzle (and also another puzzle) had actually been abandoned for a few years. There was actually a lot of cleanup work that we had to do when we first got in there.

Matt vacuuming up literally scores of insects

Matt vacuuming up literally scores of insects

The mylar was attached directly to the ground and ceiling with gorilla tape (which we discovered was much more structural than duct tape — if you ever need to hold things up, seriously don’t buy duct tape) and then staple gunned to the carpet and ceiling. We were told we could make minimal structural damage to the building because it was slated for demolition soon anyway, so we had some fun with that. The funny thing is that that building had been “condemned” since we had been sophomores, so we were sort of dubious about this whole demolition thing. Apparently they had a demolition permit for the month after Ditch Day, though. I haven’t been back on campus to check if they actually followed through on it.

Update (2013-08-02): A friend on campus tells me that the buildings are still up.

Update (2019-04-26): They finally managed to demolish the buildings a few years back. Several more years of stacks got to use the building, but hilariously had to do much more extensive clean-up work than we were asked to do.

In order to ensure that the area was completely dark, even during the day, we actually taped some black plastic to the windows underneath the mylar that ran all along the outside walls. I spent a very long time trying to lightproof the room (as usual, 90% of the effort went toward 10% of the effect), which was hard to verify because during Ditch Day construction, our schedules had shifted to be nearly nocturnal.

All the wires leading to the computer, with labels. I called it "modern art".

All the wires leading to the computer, with labels. I called it “modern art”.

The mylar turned out to be a great choice for the overall effect of the room. Due to the fact that it was so thin, it actually moved around as you walked through the maze. This is pretty creepy when walking around in the dark. I had moments when I was working in the area in the dark, and the mylar moved around for just a bit too long as I was walking around (alone), freaking even myself out. The idea for using mylar came from a friend from the class above ours. We had reached out to our mailing list (which had seniors and recent alums on it) asking how we could easily get a lot of large mirrors (at that point it was still a literal mirror maze) cheaply. Our friend recommended mylar, which turned out the be the most economical option.

Overall, this puzzle definitely took hundreds of man-hours of effort (thanks to all of the alums who helped us put up the physical components) and probably about $600-800 to build (between the electronic components, wires, mylar, and miscellaneous components like gorilla tape). It was entirely worth it, though, because everyone who went on it enjoyed it a lot and I think it was one of the main pieces of our stack that made it memorable.


Hilariously enough, the only group we’d taken through the maze (out of like five or six) that didn’t actually complete the activity was the group actually on our stack on the day of Ditch Day, even though we had playtested it beforehand. Somehow, the first time they went through the maze, someone managed to turn off one of the speakers. The second time, they somehow decided the puzzle was broken (it wasn’t). Even the group full of drunk alums (who started out by pushing random buttons at first) managed to solve it (after sobering up a little).

Next time, I’ll cover our other main puzzle: the “space alert,” or Synchrotron puzzle. It also took a lot of effort to build and I’m excited to share it, because it was equally cool. Unfortunately, I wasn’t quite as involved in its construction, so I probably won’t be able to provide as much detail unless Jeff has time to contribute.

The Vector Chrono Travel AI Interface (only for Android)

This is part 3 of a 10-part series.

Now that I’ve described the plot of my stack, I’ll start explaining the details of the physical components that the people on the stack experienced on the day of. The first component I’ll describe is the Android application that the stackees used to receive clues and information during the day.

While eating a nice breakfast at the Athenaeum, the frosh received a tablet computer from the ’employees’ representing the Vector Corporation. Upon booting the device, the frosh were greeted with a screen that looked more or less like this:


The AI Interface

The best part about the tablet computer we used? It cost $55. It’s certainly no impressive piece of hardware, but I love that we live in a world where I can buy a portable computing device that I can program for so cheap. Furthermore, as prices drop, I expect to see more of these on stacks, which can open the way to some pretty exciting demonstrations.

On the screen, the frosh could see a list of messages (which there was only one of at first) from the Vector Corporation and the AI itself, their current space-time coordinate, the current lab time (which was the same as their space-time coordinate at that time, since they hadn’t time traveled yet), the current “encryption key”, and a button that allowed them to send a “coded transmission” to Vector Corporation.

The messages served as clues and hints, telling the frosh where to go during the day. The clocks told them both the current time and what times they had jumped to. The coded transmissions were where the frosh put in passwords and other such things that they got from their puzzles so that they could receive the next clue and move on. Finally, the encryption key was mostly flavor text, although I did set up the app to send them a message mocking them should they try to send it as a coded transmission. I wasn’t sure they would try it, but it was actually one of the first things they did. I was so pleased when I saw that they had done that.

What the frosh couldn’t see is that the app was also keeping track of all of the passwords they entered and all of the messages they had ‘unlocked’ and storing it in a text file that I could check on the Caltech undergraduate-run computer cluster (the UGCS servers, for those of you who know what that is). Furthermore, the line in the screenshot above that reads “Information about the current mission will be displayed here when necessary” was a line that I could arbitrarily change remotely. It was very useful to have these features so that we could know how far our stackees had gotten on the day of. It also proved useful early on, when they entered the very first password incorrectly (having used the wrong case for the letters). On the other hand, it became all too tempting to helicopter stacker the frosh. While it was fine (in my opinion) to watch their progress, we had to restrain ourselves from sending too many impromptu messages through the app (except the snarky ones that made fun of them — those were fine), lest we ruin the puzzles or the immersion.

The application itself was built on top of Phonegap, a framework that allows developers to build an application that basically consists of some HTML and Javascript, and hook into some phone functions through a Javascript API. The result is an application that is easy to build and runs on most phone platforms. The server side code that received the status from the application and sent any remote messages that I wrote was all written in Perl. The idea for the tablet application came from one of the people who built the stack I went on my junior year, Patrick Xia. First of all, his stack had an android cell phone application which displayed the various ‘achievements’ we had unlocked by scanning QR codes during the day. Second of all, he was the one who showed me the $55 tablet earlier last year, before we had any idea what our stack was even going to look like. He even let me borrow his app’s source code to modify.

Thus, our app was built on top of his source code, which was reportedly written in a day before his stack ran (quite impressive). His application was built for a phone and displayed achievements, but not the actual clues for the day. Thus, my contribution was restyling it so that it looked more like a tablet application, updating the code so that it would work on the two year newer Android OS, removing some features we couldn’t use because of our hardware (his application used the phone to GPS track our group, as well as the microphone to listen in on our group — it was quite devious but hilarious when we found out), making the aesthetics and flavor text fit into our theme, and inserting all of our clues and hints. Since the tablet was such an integral component of our stack, it really, really could not fail (we had a backup plan but it wasn’t nearly as good). I basically didn’t touch the server side code at all, since I didn’t need to. This was fortunate, since I’m not familiar with Perl at all.

A few miscellaneous things: First, the way the space-time coordinates clock worked is that each message had a time value associated with it (or -1 for messages that didn’t travel the group, or -2 for messages that traveled the group to the current lab time). When those messages were unlocked, the app calculated the offset in milliseconds from the current lab time and the time on the message (unless the time was -1) and remembered that. Then, there were two JavaScript date objects, one of which was initialized to the current time (plus 200 years) and the other was initialized to the current time plus the offset (plus 200 years), every time the callback (which was what also sent the current status to the server and got any messages I sent remotely) was initiated. This way, the current space-time coordinates clock ran along with the current lab time clock, as you might expect.

Second, the one advantage we foresaw with having the app was that we didn’t have to spend the entire night before laying out our paper clues, since we didn’t really have paper clues. This was incredibly nice, since we could get our clues done much sooner.¬†However, all of those hopes of saving night-before stress were fruitless, despite having started our stack quite early. It’s always that last 10% that gives you trouble, as anyone who has built a large scale project knows.

On the morning of Ditch Day, not having slept, I ran into a major issue while I was entering all of the clues into the application. Since I had been working on lots of little things that night and the plot only got completely finished late that night as well, I started inserting the clues pretty late. Anyway, I ran into this bug where the Javascript interpreter was complaining about missing characters what turned out to be 30-40 lines away from where the actual issues were, but all of the code looked valid to me. After spending an hour and a half selectively removing code to see where the problem was, I was still nowhere, so I sent a desperate call for help to the Ditch Day list my class was using (and that our helpful alums were on). Fortunately, Patrick was magical and helped me discover that I had trailing whitespace in some lines where I was breaking strings across multiple lines (which was completely unclear from the errors I was getting, in my defense). I got the app completed and on the tablet with 20 minutes to go (and with my hopes for an hour and a half of sleep having turned into no sleep that night — thus leading to my having pulled my only all-nighter during Caltech). This is yet another reason to set Eclipse to remove all trailing whitespace on lines by default!

In the next post, I will describe my favorite physical puzzle on our stack, and one of our two centerpieces: the mirror maze. Unfortunately, the stackees didn’t really capture any video of themselves doing the puzzle, but the puzzle was so good that we ran it with five or six more groups over the next two or three days, so I have a video of one of those runs to show you. Until next time!

Vector: A Stack About Time Travel and Caltech

This is part 2 of a 10-part series.

Hello again, readers! I’m writing again after a great weekend where I got to meet up with lots of good friends. I’m actually quite excited to write this post, because I get to start in on the details of the stack I built and write about one of my favorite components of the stack: its plot! Since I’m so excited and since the plot/clues document we had was 7,500 words long, this post might wind up…kind of long. I’ll leave out the details of the actual puzzles and fill in as I write the posts about the puzzles themselves.

As you may have noticed from my descriptions of the stacks I went on, stacks are more often than not based on some other content (movies, video games, TV shows, or books), though it’s not required. Furthermore, most stacks will theme their puzzles and clues to their theme, but having a substantial plot is generally unheard of (at least in my time here). That’s why my last post mentioned that having a plot made our stack fairly unique.

Our stack, being a time travel-related stack that wasn’t based on any pre-existing content (something I had been hoping to do since I was a sophomore), naturally had to be quite plot-intensive. It was so heavily plot-based that one would probably not enjoy the experience if one didn’t pay attention to it at all. This was a new thing for us and most of the people we knew, so we were unsure if it would actually work out. Fortunately, the participants in the stack really enjoyed it, a fact I was elated to find out.

The plot was primarily written by my co-stacker Matt, though all three of us spent a large amount of time discussing and making sure that the plot made sense (more on that later). He really deserves a lot of credit for the sheer amount of little details he made sure were consistent (up to making sure that the group never “ran into themselves” while time travelling). I’ll relate the plot in the order that the underclassmen (heretofore referred to as “frosh”) discovered it.

Our announcements at dinner the night before (as well as a few other representative ones I chose — the overall announcements were a half hour long). Original Video courtesy of Rochelle Weber.

The date is May 24, 2213, precisely 200 years in the future. The participants in this stack, named Vector, are lucky to go on the first ever corporate sponsored Ditch Day stack, thanks to the gracious support of the Vector Corporation. The project and stack are so cool and cutting edge that many of their details are classified, including the name of the stacking senior, who worked at Vector for several summers. The participants’ luck doesn’t end there. Today also happens to be the exact day on which Vector is revealing its Vector‚ĄĘ software, running on the Vector‚ĄĘ Supercomputing Core, developed through a partnership with Caltech, which would allow humans to travel through time for the first time ever. These underclassmen get to be the first people to ever experience time travel!

The Vector Corporation, one of the many software companies that comprise the majority of the world economy in 2213

The Vector Corporation, one of the many software companies that comprise the majority of the world economy in 2213

You see, scientists have long known about the existence of quantum wormholes, but only with the development of this high-powered software running on a quantum supercomputing core have humans been able to calculate the location of these wormholes and open them up to allow for macroscopic objects to travel through. The first time machine was turned on at 8am on May 24th, so nobody can travel earlier than this time, and time is comprised of a single self-consistent timeline.

Unfortunately, the Vector lab was compromised earlier today, and the Vector corporation hopes that the Caltech undergraduates will be able to use their ingenuity and intelligence to find and interpret any clues that the stacking senior may have left behind before his disappearance.

The frosh are taken to a very nice breakfast at the Athenaeum by two agents of the Vector Corporation (in reality, two recently graduated alumni). They discuss the benefits of working at a software company after graduation, and provide the frosh with an Android Tablet running the Vector Chrono Travel AI Interface. This interface is an Artificial Intelligence who interfaces with the software on the Vector Core, provides an indication of current lab time (the time their body has experienced) and space time coordinates (the time on the timeline at which the tablet exists), and incorporates state of the art encryption for transmitting messages to the Vector corporation.

The frosh are sent to UGCS, where they find a letter from themselves in the future (signed by one of the participants on the stack, thanks to some shenanigans we pulled). The letter reads:

Hello past selves,

There is no less awkward way to put it, we are you from the future.

We did not have time to write out this letter ourselves, but your tablet AI procedurally generated it. We cannot tell you much about the situation as it currently stands, just know now that things are more complicated than you know just yet. We remember seeing this letter in the past and did not find it very helpful, but we cannot tell you the whole story or our situation will be compromised.

This is the likely last communication you will receive from us. If we succeed, time travel from our point on will be impossible, and if we fail, then we will not be around to send further messages back. Take this letter with you as you’ll need it at lunch.

Good luck, we know you will succeed.


[Stack participant signature]
P.S. We know you will succeed because we’ve already done all that stuff you’re about to do, assholes. And the code is ugcsactive.

The AI on the tablet chooses not to forward the letter to the Vector Corporation, as it does not feel that to be necessary at the time. At this point, the frosh have been jumped back to 8:01am and learn that some Vector time machines have had their access codes changed, and the stacking senior may have acquired these codes and hid them in a conventional Ditch Day puzzle that he was forced to abandon due to the building being slated for demolition. They are to go to the old Y building to attempt to recover these codes.

After they succeed in recovering the codes, Vector finds that several sabotages have occurred. The frosh must go to Beckman Institute to access confidential Vector databases in order to track down the villain. However, the decryption algorithm for the database takes a long time to run (it is brute forcing in BQP), so the group must split up into two rooms. One group has the initial state of the computation and the other group, which has traveled several hours in the future, has the final state. The two groups must communicate their states over a Skype call and coordinate to obtain the correct code.

After completing this task, the frosh are jumped back to the current lab time, obtain a flash drive with some necessary information and hand it off to a Vector Agent (played by yet another recent alum, Kurt) in the SAC. However, they are not allowed to leave the building with this flash drive: while the building is open for any member of the Caltech community to view the documents, they may not remove them from the building, and there are two security guards (also played by recent alums) on the level that the frosh are located. The AI tells them they must use their “human cleverness” to remove the drive and points out that the fourth floor has a balcony.

Once the handoff is complete, the frosh are told to proceed to SAC 15 to make their next jump. Unfortunately, once there, they discover that someone has sabotaged the wiring in the time machine and they must fix it. By the time they finish fixing it, they find that they have missed their jump, and that the AI has instead jumped them to 8:01am, yet again. The saboteur has been tracked to the North end of the same Old Y Building they were in before, so they should head over there and attempt to capture him. Strangely enough, there are signatures coming from the building similar to those around a time machine.

When they arrive, an Artificial Intelligence informs them that a time travel protocol has been activated and that there are twenty explosive devices currently coming for their space-time coordinate. They also hear voices off in the South end of the hallway. Wasn’t this about the same time they were in the South end of the building? The voices do sound familiar.

Emergency protocols activate to send said devices forward in time if they do detonate, but all twenty must be disarmed by the group before they can proceed. Even after the successful disarmament of the devices, scans are unable to indicate the origin of the devices. They only know that a Vector agent will need to jump them again before they can get back on the trail of the saboteur, who appears to be trying to assassinate them now. Right now, it is time for lunch.

After lunch, they are sent to find Kurt, the same agent to whom they handed off that flash drive, in Karman. He will jump them to their next location. When they arrive, they find that Kurt has been tied up in the meeting location. He looks confused and asks why they are untying him, since they had just tied him up. The frosh are, of course, confused, but Kurt tells him that he’s surprised that they’re even there, since Vector tried to kill them twice. He tells them that since they (the frosh) stole the flash drive from him, he’s screwed and Vector is going to try to kill him too, so he might as well work with the frosh. The frosh are once again confused: in their timeline, the last time they saw the drive was when they handed it to Kurt right before lunch.

Once Kurt realizes that he has mistaken the temporal identity of the group — he thought they were the ones who had just tied him up — Kurt reveals that Vector is trying to sabotage Caltech for a nefarious plan which involves stealing important secrets from the school and that it is imperative that they shut down the Vector Core to prevent the plan. The villain that the group had been chasing all along did not exist, and Vector was using this “villain” to manipulate the frosh into furthering their plan. The senior who built the stack embedded some clues about this in the stack, until Vector found out and disappeared him. Kurt remembers just the code ‘g o o’ and hopes the Chrono Travel Interface is able to send the frosh to what they need to do next. He also reprograms the AI to stop reporting to Vector Corporation, which has the strange side effect of giving it a more quirky personality.

Kurt’s amazing acting, as captured by the participants on our stack.

They are jumped to 9:45am (having the interesting property that this is the only version of them walking around at this time despite it being about 2pm lab time and their having spent all day travelling through time) and sent to Blacker Beach to find¬†acrylic¬†chips containing the next code in a mysterious goo. Once this code is obtained, the AI finds that the Supercomputing Core is in the Synchrotron lab at Caltech. Of course a quantum computing core would be in a physics building! But first, the frosh must tie up some loose ends. It turns out that they were the ones to sabotage the wiring in SAC 15, because they were about to be jumped into a trap. Furthermore, they are the ones who must steal the flash drive from Kurt and tie him up so that he will reveal the Vector plot to them. Of course, the Kurt at that spacetime coordinate doesn’t suspect a thing.

The frosh must also sign that letter to themselves that they received earlier in the day to avoid a “nasty paradox.”

Next, the AI travels them back to the current lab time so that they can meet up with Kurt and destroy the Vector Core (note that this required Kurt to go from being confused, to fighting them, to helping them all within a few hours. Kurt deserves so much credit for being an amazing actor). In order to access the core itself, they must perform a very complicated security override on the structure that houses it.

Once they complete this override, two Vector employees (two more recent alumni) run in and order them to stop. The frosh and Kurt must escape through an alarmed side room in Synchrotron. They must move quickly, for the Vector employees are putting on a good chase! Once out, they proceed to Blacker Courtyard to dispose of the core the only way we know how — by destroying it in a furnace. The core was made of a rare exotic matter, so a new one could not be developed for several years.

The frosh are left with this message from the AI:

Congratulations, Vector has been exposed as an evil organization and time travel has been halted for years. This is more than anyone could have asked of any undergraduate.

Now that the seniors are ghosts, only our legacy can remain here at Caltech. Do awesome, and continue to make great traditions like Ditch Day happen. If people really try, maybe in hundreds of years there will still exist cool places like Caltech.

We’ll try to meet you in the courtyard, but you all should probably think about showering before dinner.

In the next post, I’ll discuss the actual Android app (the Vector Chrono Travel AI Interface), which acted as the group’s primary method of receiving clues and information during the day.

Special thanks to Matt and Jeff, my co-stackers, for reading over this post for accuracy.

What is Caltech’s Ditch Day?

This is part 1 of a 10-part series.

Whew! I write to you on the other side of 38 quite hectic days. Since my first post, I had a great four-day vacation to Las Vegas, packed up literally everything I owned, graduated from Caltech, became a California resident, drove up to the Bay Area, moved into my beautiful (albeit overpriced) San Francisco apartment¬†(edit: I don’t live there anymore as of October 2013 — my new place is much nicer and much more overpriced), bought a bunch of furniture, and started my internship at Sift Science.


We look so happy to be leaving all of our friends! Source

Now that I have some time to write again, I can finally start off my 10-part Ditch Day series by explaining to you what Ditch Day actually is.

As I said in the intro post, Ditch Day is not what you might think given the name. The seniors don’t really ditch in the sense of going to the beach and just relaxing all day (even though I’m pretty sure we’d all have liked to). They do have to leave campus, because any senior spotted on-campus will be duct taped to a tree, and classes are officially cancelled for everyone. The latter is because each group of seniors has built an entire day of entertainment, activities, and puzzles (overall referred to as stacks) for the underclassmen to enjoy all day.

On my very first Ditch Day, I worked for an Aperture Science-esque company, where I participated in experiments testing senses and “super-senses”, including taste (having to solve a puzzle with custom-made “tasting gels”), hearing (having to shut off speakers playing the Ride of the Valkyries in a loud and dark room by pushing buttons next to them), pain (having to lick nails connected to a 9V battery to see which were live), balance (having to balance a gigantic suspended metal mobile with our whole bodies), and super-tasting (eating sour food under the influence of Miraculin). More details about that stack are in a blog post¬†written by one of the creators of that stack.


The sign-up poster for “Sense”, the stack I went on my frosh year.

The next year, I was part of a real life version of Achievement Unlocked.¬†We were given an Android phone with an application at the beginning of the day that gave us updates on the achievements we had earned as we solved puzzles such as a 3D minesweeper puzzle (which involved lots of boxes in a room), lifted boxes with QR codes on them with one of the official Caltech construction cranes, and played with a mural in our house that used hidden capacitive plates to respond to touch with sound. Little did we know the Android application (and by extension, the seniors who were stuck off-campus) was listening in on our conversations with the phone’s microphone.


Operating the crane (with wooden claw attached) that we were allowed to use as part of “Achievement Unlocked”.

For my last Ditch Day (on the going on stacks side of things), I went on a Calvin & Hobbes stack, where we hung out in a tree house (no girls allowed!), traveled through time while solving a puzzle that required the use of our safety goggles (3D glasses), and solved a Slitherlink puzzle that had been created in the real world rather than on paper.

ImageWe also “caught” these amazing Hobbes backpacks.

Other awesome stack elements that come to mind are a giant ice wall that people could climb on and a laser maze in the tunnels, and this is all just things that happened while I was there!

Ditch Day wasn’t always this way. A long time ago, Caltech seniors did just ditch classes and go to the beach. The underclassmen thought this was rather unfair, so in true Caltech style, they began pranking the seniors’ rooms. Soon enough, the seniors began to develop counter-measures for pranking while they ditched. These ranged from placing giant concrete barricades and steel plates on their doors and windows to offering the underclassmen bribes (in the form of some cool or expensive things). I’m sure the bribes eventually became things like paying for cool adventures for the underclassmen. Eventually, things escalated to the point where seniors would build these massive elaborate stacks.

As an underclassman, Ditch Day is pretty much the best day of the year. When I was a frosh, I was told that it’s “better than Christmas!” The seniors pretty much spend all of their time from about April (and sometimes much, much earlier) until Ditch Day (toward the end of May) working on their stacks, and it’s always great to see what that much effort out of some of the smartest people in the country can produce. The fact that classes are officially cancelled so that we can do this is especially awesome. However, as an underclassman, we never know when Ditch Day will be! The date is a heavily guarded secret. If you ask any senior, they’ll tell you that “Ditch Day is Tomorrow!” at any point in time, even the newly-minted seniors immediately after the end of the previous Ditch Day — at 5pm, when the cannon fires, the juniors become seniors and the seniors become “ghosts”.

To make things even more complicated, the seniors often hold fake Ditch Days — they’ll make a set of announcements at dinner and even put out stack sign-up sheets the next morning. However, these stacks give you around an hour of content until they tell you “go to bed frosh, Ditch Day is Tomorrow!” By the time announcements are over, and definitely by the time you see the sign-up sheets, it’s generally clear that this is a fake Ditch Day (unless it’s the day before the real Ditch Day and the seniors are trying really hard to fool the underclassmen). However, even the fakes are valuable because they give everyone much-needed logistics practice (when to start waking people up, how to sign up for a stack, what the rules are about signing up, what kind of clues to expect on a stack, etc.) and they are pretty good fun to boot. When the class one year above mine became seniors, I went on a Lonely Island themed stack for their first fake, which involved blasting Lonely Island music around campus at 8 in the morning among other things. For a fake Ditch Day from another year, I got to play a mini laser harp.

On the senior side of things, we get (have) to spend all day being on-call for our stacks, in case an activity fails and we have to cloak-and-dagger our way to campus to fix it, or if they can’t solve a puzzle. In my house, we are always lucky to have a readily available army of recently-graduated alumni who are around to keep things running smoothly, or at all. What we’d really like to be doing is sleeping all day, though, since we just spent a week getting minimal sleep and probably pulled an all-nighter just before. The 90-10 rule definitely applies: I spent the night before doing all sorts of random menial things, like cleaning up some areas we had puzzles in, and debugging some terrible Javascript errors. As a result, a night in which I thought I’d get three or four hours of sleep because we were so ahead in building became a night in which I pulled what was possibly my only true all-nighter at Caltech.

As a senior, you also realize how supportive some departments are of Ditch Day and of students doing cool things in general. In our case, the physics department let us use and have after-hours access to a pretty big space in their large warehouse/lab that contained a lot of expensive equipment for construction and housing of a puzzle. I say some, because some blatantly aren’t. I’m looking at you, Geology and Biology. Both of them wouldn’t let us have the use of classrooms on a day when classes are officially cancelled. Either way, it’s nice to have some evidence that some people are still for keeping the spirit of Caltech alive rather than just paying lip service to the concept.

Overall, if you take away one thing from this post, it’s that Ditch Day at Caltech is a¬†big deal¬†and it’s where a lot of very talented scientists and engineers get to do amazing things. In the next post, I’ll introduce the stack that I spent several months building and one of its most integral components: the plot. Ours was unique of all the stacks that I had seen in that the plot was so important to one’s enjoyment of the whole experience, but I’ll explain that next time.