Future Tense

How Chess.com Built Mittens, the Evil Cat Bot Destroying Players’ Souls

Three cat avatars above a chess set.
Mittens (center) and some other brutal chess cats. Photo illustration by Slate. Photo by sk/Unsplash.

Not too long ago, chess-playing computers—the supervillain of many a human grandmaster—were as intimidating physically as they were virtually: bulky, sturdy, sleek, jet-black monoliths in miniature, programmed to crush chess hotshots instead of spurring evolution. Such megaminds, imposing as they were, were also christened with futuristic-sounding names: Mac Hack, Cray Blitz, Deep Blue.

Having won the war against the human mind, these coding wonders are now a ubiquitous, and mostly embraced, part of today’s chess industry. All of which is to preview the latest virtual robot to confound the greatest minds of our time and throw the entire chess world into pandemonium: a 1-point-ranked kitten named Mittens.

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That’s right, folks. Decades of wondrous progress and technological development have brought us from MANIAC to Mittens. The new digital scourge of grandmasters everywhere—and boon for Chess.com’s metrics—is just one part of an ongoing tradition for the wildly popular Chess.com app: a monthly rollout of custom, automated, well-skilled chess-playing bots that any user can take on, however unsuccessfully.

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Online bots have been a key part of Chess.com, with easy programs for training and instruction as well as bots meant to play in the styles of chess celebrities. But the crazy-making viral fame of Mittens is something else. Despite its purported near-bottom ranking, that kitten is the most difficult opponent of the January slot, which includes a beginners’ bot called Scaredy Cat, relatively easy level-ups with Angry Cat and Mr. Grumpers, and a Garry Kasparov play-alike known as Catspurrov.

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Chess.com has been offering monthly, gimmicky bot options like these since February 2021, when it rolled out a slew of bots that represented The Queen’s Gambit’s protagonist, Beth Harmon, at distinct ages and levels of chess aptitude. Although these bots are now gone, to fans’ chagrin, Chess.com has offered several novelty bots over time: one modeled after the killer robot doll M3gan, a trio of “mom bots” for Mother’s Day, even a quartet of soccer teams.

To learn about the Mittens craze, the process behind constructing a good chess-playing bot, and what the chess bots craze symbolizes for the longtime clash between human grandmasters and their computerized nemeses, I spoke on the phone with Colin Stapczynski, director of written content for Chess.com and head of the bots team. Our conversation has been edited and condensed for clarity.

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Nitish Pahwa: What inspired you to kick off this trend of novelty chess bots?

Colin Stapczynski: Chess.com’s explosion started with the [pandemic] shutdown, and then the first Pogchamps tournament. The show The Queen’s Gambit took it to a whole new level. So, I got a message from Erik Allebest, our CEO, saying: “I need your help, we’ve got to write some bot statements for Beth Harmon.” I was really excited to get that done. I’d been working on our bots from the beginning, but that was the first one that essentially crashed the servers. There were so many people wanting to play: We’re talking hundreds of millions of plays and games played against those bots.

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Since 2022, we’ve been seeing a new wave of interest for chess. We’re hitting more new daily signups every single day, and we passed 100 million members pretty close to the end of the year. It’s obviously not all the bots, but I do think the bots are part of that. Mittens, specifically. We had a feeling that the cat bots—which will be around for the month of January—would be pretty popular. Who doesn’t love cats? We thought that would be pretty big, and we expected that Mittens would be the most popular.

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These bots are usually around for a week or a month, then they’re gone. I’m curious about why that is.

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We decided to have what I think of as a carousel of bots, to keep the options fresh and to keep people interested. Sometimes we bring them back, like with the holiday bots. We launched those two years ago for the first time, and when they came back this December, they still got almost 70 million plays. Halloween, we had the zombie bots. In November, we had the fake billionaire bots, which were also popular. Those had a little fewer than 50 million plays that month. In 2022, there were over 1.5 billion games played against all the bots combined.

When something like the Beth Harmon or Mittens bots reaches mainstream media, that’s one of many signs that we’re doing something correct. We have a hundred million members, a very diverse set of people. How do you keep chess fun and exciting for such a large group? It’s tough. Sometimes we’ll go with cat bots, which are appealing to a very large audience. Sometimes we’ll get more specific and poke fun at some billionaires—why not? When we have fun with it, our users have fun with it. That’s a really important combo we’ve picked up on.

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How much effort does it take to code these bots or train them to the specifications you’d want in time for a launch?

It can take quite a long time. There’s a backend team that’s created an interface for the writers and myself to use in order to create the bots, test them, make sure the statements are working correctly, assign their personalities and playing styles and ratings. Every detail has to be taken into account. There are bots that are planned long ahead of time, then there are bots that come pretty quickly when the company’s like, “Hey guys, we need these bots by X date.” That’s an all-hands-on-deck type of moment.

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First, you have the ideas. Who should have a bot? Who wants a bot? We get bot requests all the time from chess players, chess streamers, celebrities, all over the place. From the time that we have an idea and a bot is greenlit … depending on the bot and the complexity of the bot, sometimes all of it could be done in a couple of days. Sometimes it’s done over a course of four weeks. It always depends on the urgency of the bot.

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I can’t help but think about the long clash between human and computer chess systems. These bots—which are more powerful and less resource-intensive than the computers that played big matches in past decades—they seem to be pretty frequently celebrated. You even have grandmasters engaging with them. I’m curious about what you think has helped drive that shift in chess culture.

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I could talk about this for days. Chess’s relationship with computers, engines, neural networks, I would label it as love-hate. Mikhail Botvinnik, former world champion, studied computers in the ’50s and ’60s, and even back then saw the importance of the machines. This was even before superengines, which the chess world loved at first, but then they posed this almost existential crisis. Oh no, what do you mean Deep Blue defeated Kasparov? Is the game over? I’ll never forget when AlphaZero stepped onto the chess scene and had a private match with DeepMind. Google had created this bot, AlphaGo, that defeated the world champion Go player, and then set sights on chess. They didn’t even have the bot play a human. They had it play Stockfish, which was—and still is—the strongest chess engine that people have access to. It’s open-source, anyone can use it, any website can use it. When AlphaZero stepped onto the scene and essentially destroyed Stockfish in the match, it shook up the entire chess world.

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Engines are, without a doubt, stronger than the strongest human player. And of course people care about chess players because they’re still people. This is Chess.com having fun with that relationship. Bots don’t need to be these big, scary, intimidating entities that we don’t understand. On Chess.com, we use bots for many different things, not even just the bots that anyone can play. We also use them for our coaches product. We use it for Game Review and analysis. Engines should be a tool to help improve a human’s understanding of chess. They’re also something we can have fun with. If you’re a streamer or a chess personality, why wouldn’t you want a bot on Chess.com and have millions and millions of people play against it?

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Out of all the bots you’ve done since Beth Harmon, which has been your favorite, or at least been the most fun for you and your team to take on?

Oh gosh, that’s a really tough one. I’m going to duck the question but discuss the invention of Mittens, if that’s OK with you. The bot writing team is very talented: Pedro Nami, Nathaniel Green, and I wrote a lot of the bots. And then Sean Becker, who’s the newest addition to the bot writing team, he was the one that really took the reins for Mittens.

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We get this assignment, that we’re doing cat bots. We have all of these great internet meme cats selected, Marija Casic does the avatars, they look wonderful. Now it’s the bot writing team’s turn. OK, we’re doing five bots. Sean, take this one, Pedro, take these couple, Nathaniel, you take this one. For the the first draft of Mittens, the question from Sean—I won’t forget this—he said, “I don’t know if it should be like an Ivan Drago, ‘I will crush you’ type of personality, or just a super cutesy thing laughing at everything you do, like no matter what the player does, it just bats it away with laughing.”

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It didn’t take long at all, less than a minute of discussion between the team, before we decided, why not both? That’s where Mittens’ personality was born, where it could say these profound pseudo-existential quotes, busting out an Oppenheimer quote, all those really hard-hitting lines that make users go, “What did this cat chess bot just say to me after I put it in check?” All of the bots are collaborative like that.

Seeing some of these streamers playing against their own bots is just comical. Levy Rozman—the biggest YouTube content creator in the chess space—he really loved Mittens and made a lot of videos, which was unsurprising. But I won’t ever forget the first time he played the bot we’d made for him on stream. Every time his bot said any statement, he just kept saying over and over; “Who writes these? Why is my bot saying this?” While you’re writing these bots, you don’t know how much fun it will be for users.

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What’s the process for grandmaster bots, like for Hikaru Nakamura? Are those trained on their games and streams or personal Chess.com data over time?

I would say that each bot is slightly different. With grandmasters, we know their differing playing styles, we know the openings they play, and then the question is, how much material do we have on something fun they’ve done? Some have more of a social media presence than others.

We do our best to go as in-depth as we can to get their playing style and strength as accurately as possible. The ratings that are displayed are as close as we possibly can get them to the engine strength as well as to their playing style. It’s not a simple, quick assignment. These are decisions that take a lot of deliberation. The last thing we’d want to do is put out a bot that’s incorrect or not true to the person, or, the absolute worst, isn’t fun to play against.

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Working on the bot for Anish Giri—he’s a top 10 grandmaster—he’s amazing on Twitter, a hilarious person to follow. Pedro wrote Giri’s bot and had fun with that one because there’s so much source material. I worked on Hikaru’s bot. Obviously, Nakamura has a wealth of fantastic source material because he streams all the time and is creating fantastic content on YouTube. For this young grandmaster from Uzbekistan who was the 2021 world rapid champion, Nodirbek Abdusattorov, our writer was such a big fan of Abdusattorov that he was able to bring that one to life. When you’re a chess player and you’ve followed these careers, you pick up these details about the grandmasters that others don’t see, and you can sneak them into the bot statements here or there.

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We started doing streamer bots because Pogchamps was so big. We had a lot of time to work directly with the streamers: Mr. Beast, xQc, Ludwig. Some streamers want to be very hands-on with their bot’s theme; they want to know what their bot is going to say or where they might even help in that writing process, while others are just like “Run with it, whatever you want to do is cool with me.”

I’m curious what direction you take when it comes to something like the holiday bots or M3GAN, where the character is not a typical chess figure with a long record of games. Where it’s a character you’re conjuring based on how you perceive their chess-playing ability.

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When we’re working on something more abstract or not a real person, like the M3GAN bot, we have far more creative control. We were working on the M3GAN bot before the movie was even out. Most of those bot statements were created using the two trailers. With this A.I. doll, her main objective is to protect this little girl, and she does it at all costs. So maybe she starts protecting our users from the cat bots. M3gan version one is very kind, very nice. She’s protective. The bot statements reflect that, as does her playing style. She’s more fun and has an open, beginner, friendly playing style in terms of repertoire and rating and strength.

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As she progresses toward becoming evil, we had to give her a more aggressive playing style and opening repertoire. Obviously, her strength changed drastically. It created a life of its own. M3gan and Mittens had a 150-game match for the Computer Chess Championship, with quite a few people watching. At different points, M3gan was winning or Mittens was winning, then ultimately, Mittens defeated M3gan, and the cats came back because cats have nine lives.

I’m curious how you thought through the interoperability of pitting bots against each other. Do you have bigger plans in mind for bots-versus-bots and how it might be useful for bot training?

The Mittens-versus-M3gan match opened our eyes a little bit more to this idea of bots playing bots as a spectacle. I can’t say we will or won’t be doing more of that in the future.

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The point of the bots is for our members to have fun and enjoy chess in a new way while also trying to grow the game. When you’re playing a bot, it’s solely for the love of the game., it’s solely for fun, it’s solely for enjoyment. The original intention of the bots was fun, enjoyable chess anywhere you are—doesn’t matter if you’re standing in line at the bank or if you’re on the subway or on a plane or at home. And there’s something for everybody. If you’ve been playing chess for a long time and you love cats, try Mittens. If you just started playing chess and you love cats, you’ll play Scaredy Cat. That’s what chess is about. Chess is the most popular game in the world for a reason because anyone can play it, and we want that to be reflected with our bots.

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