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.