
Alumni Chats: Justin Yu
Justin Yu, or fractal161 online, is an accomplished Classic Tetris player. The former Mathlete is the 2023 Classic Tetris World Champion, the second person to ever “beat” the game and the first person to achieve the earliest possible game crash. Justin is a senior at MIT earning his bachelor’s in computer science and math, with a minor in music technology.
We talked with Justin about parallels between math, music and video games, and the value of community.

September 2024
I think a lot of us are familiar with Tetris, but Classic Tetris is a bit different. Can you tell us about it?
I think it can best be described as, for example, the difference between a highly produced studio recording of a song versus an acoustic version. Classic Tetris is similar to the acoustic version: it’s stripped down and focuses on fewer mechanics, but pushes those mechanics much further than they are in other variants of Tetris, where you have a lot more mechanics and a lot more ways to explore.
How did you choose your username, fractal161?
The fractal part comes from a Vihart video. Vihart is this really great YouTube channel that talks about recreational math, and she had made a number of videos about fractals so that was present in my mind. And 161 is the first three digits of the golden ratio.
You said once that the learning curve for Tetris is “steep and punishing.” How did you get good at it?
I think it was a matter of putting in the hours. Much of the punishing part is the feeling of not knowing whether you're improving, and the only way to get through that is to move forward and get more experience. So, I do think that just about anybody could do it with enough practice and hours. It's just committing yourself to going through the process in the first place that’s the biggest challenge.
New techniques, like the rolling technique, can push the boundaries of the game. You were one of the first players to use it. I’m wondering how you split your time between mastering existing techniques and trying to develop new ones.
I was one of the earlier members of the community who had begun to make the switch, but I still did it several months after it was first introduced to the world.
There’s a fairly even split between physical aspects of playing the game, like moving the pieces where you want, and the mental aspect, which is deciding where you actually want to place the pieces. With new techniques, you’re able to expand that even further. I would practice a bit of both techniques in the early days, focusing exclusively on just the technique of rolling as opposed to trying to play some games. I didn’t really know what I was doing. And then when I wanted to practice, I’d just play normally, the way that I had. I worked on those side by side, then once I did feel like I was comfortable enough with rolling as a mechanical process, I started switching over to that. Now it’s more or less everything I do.
What does the process for developing new techniques look like? Is it fairly collaborative, or more of a solo endeavor?
It's a mix of both! There are solo elements, for example, when Chris Martinez (cheez) first had the idea to roll on the back of the controller. That completely changed the game. But there's a lot of collaboration too, like how we share different grips and practice strategies with each other.
How has Tetris helped you develop skills in programming?
The game is written in this old assembly language called 6502 assembly, and in order to understand the mechanics of the game at a certain level, it helps to know how this language works. So, I was motivated to learn this language that is, in all other aspects, pretty useless because I wanted to understand how this game worked. Once I did that, I started working on things called ROM hacks, which is sort of injecting your own code into the game to give it different mechanics. I've made a couple of practice tools as a result of this.
For more traditional software, there’s a lot of infrastructure in the scene that is perpetually in wants of people to maintain it. I've naturally been exposed to that and want to be more involved. Being part of the community has helped me develop skills even more than the playing itself.
How far can the limits of the game be pushed? Now that you’ve “beat” the game, what’s the next challenge? Or do you move onto something else entirely?
A lot of public perception of our game has been driven by this idea of beating the game and setting new milestones. But at the same time, arguably the biggest component of our community is that we play, we have competitions, we play head-to-head matches.
And there are other achievements to pursue. One guy played what was essentially a perfect game, getting all the way up to a million points using only tetrises, which was seen as basically impossible because of how random the game is. There’s a milestone called rebirth where you cycle through all 256 levels and go all the way back to zero. There’s this one level that, because of some bug, lasts for 800 lines instead of the normal tendency, and nobody’s been able to get past that.
There is a lot, and I think the more you come to understand this game and how it works, the more you realize just how much there is.
You hosted your own Tetris event at MIT earlier this year. What was it like to experience a tournament as an organizer and not a player?
I think in some of the pictures during downtime, you can see me sitting in one of the chairs just completely knocked out. That kind of describes my experience with the entire thing. I didn't know what I was getting into. I was pretty overwhelmed and was able to make it through with the help of a lot of other people who know way more about the finer details of running an event than I do.
But I wanted to try out something new, and I think I ended up succeeding on that front. We're looking to hold it again in January. I have a lot of respect for the work that goes on behind the scenes. To link it back to MATHCOUNTS, planning competitions and having activities planned…it’s a lot.
That’s something I’d like to keep exploring. It was worth it. There were a lot of people who flew in from out of Boston, even one person from the United Kingdom. And these are all people that I’ve known for many years.

Along with computer science and math, you’re also studying music technology. What about music technology interests you most?
It’s a fusion of two things that I like very much: computer science and math. I’ve played cello since I was in fifth grade. I've listened to a lot of different music and different genres, and with music technology there is this opportunity of using my knowledge in both fields to create unique experiences, and I think that's really interesting.
You play cello in the MIT Video Game Orchestra. What makes video game and film music distinct and special?
It’s what we grew up with. One of the core principles of our group is that all arrangements must come internally, so people who are with us or associated with us have to arrange everything. We'll listen, practice and make adjustments for two or three months up until our concerts. And because people are submitting the arrangements themselves, they're picking the stuff that they like and the stuff that they grew up with. There's one member who is known for arranging Pokémon songs who has been with the group basically since the beginning. There's another guy who's focusing on a game series called Persona. You get to see a lot of people’s different backgrounds in a sense, and their passions come through in the music we perform.
Do you have a favorite video game/film/anime soundtrack or composer?
I think, as a basic answer, I'll say the music of C418. He made the original music for the Minecraft, which is funny because I’ve never played Minecraft. But I like the music a lot. I’ve listened to it on repeat many, many times. I guess in terms of games that I’ve actually played, there’s a series called Kingdom Hearts that has a lot of really nice music, some orchestra and some synthetic. There’s a lot of nostalgia there.
How do you incorporate math into your creative interests, like music or video games?
Being involved in the Tetris community has been a driving force in my personality and how I approach new challenges. I feel pretty unique in the community with regards to what I’m experimenting with and what I’m trying out. I tend to play more non-standard versions of the game. I try to practice it in as many different ways as possible. And a lot of that comes from thinking about what the building blocks are for all the aspects of the game, and then isolating them and drilling them over and over.
I see a lot of similarities in how I prepared for math competitions in the past. Break down tricky problems into multiple parts and figure out how they work together. Practice areas you’re weakest in, even though it feels better to work on areas you’re strongest in. Go with it and see what happens.
Do you have any favorite memories from MATHCOUNTS?
I think it's got to be the national competition. I didn’t expect to perform as well as I did in the state competition that year, so it was a surprise to me that I was able to make the national team. I had to do a lot of work to prove to myself that I could keep up with my other teammates. It was probably one of the most intense practice regimens I've ever had. We met for the entire weekend to drill rounds and work together, and I got really close with my team members, Luke, Andrew and Ben. We became the first team to have all four members qualify for the Countdown Round. Realizing that was about to happen and winning the team round on top of that, it was a really great feeling just seeing everything come together and pay off in that way.
My experience in MATHCOUNTS shaped a lot of my high school career. I met people that I saw a lot more in the upcoming years, and a lot of that has contributed to establishing my place in this world.
Having been part of the Tetris and Mathlete communities—both fairly small and close-knit—what have you found to be most valuable in creating a positive experience for players?
I think it’s having the opportunity to participate in events and maintaining a space where people can talk about Tetris and life. A lot of really strong friendships have been formed as a result of people coming together because of this game. In terms of facilitating those experiences, I think it’s important to listen to what people want to see. Putting the community first is the most important because, ultimately, I want everyone who plays Tetris to be happy with the game. It’s really hard actually, because it’s such a frustrating game, but we make it work. We have for years, and I think we will continue to do so.
Do you have any advice for Mathletes?
The most important thing is to make sure that you are having fun. It’s a legitimate advantage. You will be more motivated to do the necessary work if it is fun. I think if you don’t feel this way, it’s perfectly fine to find another activity. Explore. There’s no right or wrong way to take advantage of this time in your life, provided you’re seeking out opportunities in one way or another. Parallel to that, take breaks. Take time to be involved with other people because that’s what you’ll remember more than any of the results or achievements. When I think about MATHCOUNTS, I remember less about the fact that we won than I do about how I felt celebrating with my team. That’s a memory I wouldn’t want to replace.
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