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.

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.

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 😛

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.