How mods made The Binding of Isaac a phenomenon, and why Edmund McMillen's laying it to rest

On April 30, the last official add-on scheduled for The Binding of Isaac: Afterbirth+ was released. Booster Pack #5 contained 'The Forgotten' and a treasure trove of bits and bobs, including "White Poop, a new poop type." It's been quiet since then. For the first time since the original incarnation of the randomly generated gross-out dungeon crawler was released in 2011, it seems like Isaac may finally get to rest.

At least, in game-form. "There's a lot of little things I want to add and that I really want to explore with the IP that I haven't been able to because I've been mostly just working on the game," Binding of Isaac co-creator Edmund McMillen tells me. "Without revealing too much information, yeah, there's stuff on the horizon."

I didn't think Steam would be interested or even allow Flash games on Steam.

Edmund McMillen

Isaac and he have now been together for the bulk of a decade, a period that's seen all kinds of change in the games industry and in his personal life. Isaac's come to symbolize the kind of auteur-driven success many enter the medium to obtain, with the kind of longevity major publishers fall over themselves to replicate. And it all started with a two-week game-jam.

The origins of Isaac 

Wanting to take a vacation post-2010's Super Meat Boy, McMillen chose to stay home and make a quick passion project with friend Florian Himsl as a way to unwind. Two weeks gradually became three months, and friends started telling them they should consider making the thing into a proper release. "It was just one of those situations where everything clicked together and it was too hard to put down, but I also didn't see any means of actually selling it," McMillen says, "because at the time it was Flash and I didn't think Steam would be interested or even allow Flash games on Steam."

Indie distribution was still finding its feet, and they considered simply selling the IP to someone like Adult Swim for a big down payment. However, encouragement from those in the know pushed McMillen to overcome his assumptions and reach out to his contact at Valve to see if Steam would give Isaac a look. Thankfully, they did, and soon Isaac was available to the world.

But back then Isaac was a very leftfield piece of work. Nowadays its core elements are common, but in 2011 the response was muted. Review scores were decent, but nobody really seemed to get what was really on. "They just kinda put it aside, it was a lot of 'oh it's like a remix of Legend of Zelda, and it's pretty cool,'" McMillen says. "It was like, OK, well, I don't know how I'm supposed to sell this thing."

It wasn't until Let's Plays latched onto the game that things started to snowball. Hours of videos demonstrating the ever-changing longplay aspect of Isaac on YouTube generated a sudden spike in interest. McMillen remains at a loss as to why people enjoy watching it, but the benefits were quick and significant. "100-200 copies, 1,000 copies a day—that summer, the first summer after release, which was probably nine months after release, is when it just exploded, and it just kept climbing higher and higher and higher."

Little did he know that a steadfast community was forming, and that it would prove integral to Isaac's longevity. Ryder Hicks, owner of The Modding of Isaac, was one of them. "I had some friends on Steam that were playing it and I was like 'What is this?' and I watched the trailer and it was very bizarre," he says. "And I was like 'all right I gotta try this' and it was amazing."

The Modding of Isaac is a community forum for fanmade Isaac creations. Through the 2014 remake The Binding of Isaac: Rebirth and beyond, modding it has become easier and easier, drawing in more creators. Hicks had run a modded Team Fortress 2 server for years, and wanted to help this community grow in the same way, working to preserve mods and encourage their creators. "It's so easy to mod and add stuff that you think might be interesting," he says. "If you're like, able to theme it in properly, you can make it some pretty cool stuff by yourself, not really having to put in a whole lot of work."

The modding scene blindsided McMillen, but has since become vital to The Binding of Isaac. The-Vinh Truong, aka '_Kilburn', now an integral Isaac team-member, began as lead designer on one of the biggest mods, Anti-Birth. "Initially I didn't want it to be anything too big, just a few items and enemies, and then Afterbirth came out and we hadn't finished our mod yet," Truong says of Anti-Birth. "But we saw what that added and thought maybe we could use this as an opportunity to show what we could do."

When people ask what would you do to improve the game, there's a bunch of stuff that I would do. And I probably say that the first thing that I would do is strip out the story bosses

Edmund McMillen

Anti-Birth is a testament to how inspirational Binding of Isaac has been. It's a massive slab of new stuff, containing intuitive bosses and clever items built by Truong and his friends in their spare time. During our interview, McMillen can barely restrain himself from singing the modder's praises, going so far as to call him the best collaborator he's ever had. "There's a lot of great modders out there, but he's on a whole other level," McMillen says enthusiastically. "I feel like he understands me in a way that I'm not completely aware of yet." Truong is considerably more modest: "[People] don't always get what the game is supposed to be like. I'm not going to pretend that I do, but I try. I guess I do my best."

The following of Isaac

At this stage, McMillen is very aware of the crossroads facing Isaac. The free updates were becoming more and more elaborate, and the question of a sequel has been looming. The additions contained by Booster Packs were starting to make their way uncomfortably close to his list of ideas for a sequel. Ending the updates now is as much about putting a formal follow-up into perspective as anything else. 

"When people ask what would you do to improve the game, there's a bunch of stuff that I would do. And I probably say that the first thing that I would do is strip out the story bosses," he says, on the subject of possibilities for number two. "Like, after you get to a certain point in the game, no more story bosses. No Mom, no Satan, all those dead-end bosses. Then I would design bosses that are more difficult and randomize them into those slots, and then you'd have a more random experience. That's where I'm heading just for a base level design for a sequel."

The current game is now at a critical mass, as he puts it, and any more big additions would require uprooting the carpet and taking down the upholstery. It would require another re-design, when a blank slate with new foundations makes more sense. After the troubled development of Afterbirth+, during which Edmund was absent for four months due to personal issues, he's keen to make sure everything they put out is as consistent and worthwhile as possible.

The ending of Isaac 

Though he loves The Binding of Isaac and loves working on it, it eventually became work. After several years of various ups and downs professionally and personally, McMillen was ready to quit games and take his life elsewhere, a feeling he dealt with in a familiar way—by making a game about it. "The End Is Nigh was by far the most cathartic experience I'd ever had," McMillen says of his macabre 2017 platformer. "I was ready to be done with games. I just wasn't getting what I have gotten out of it. I just had a bunch of terrible experiences when it comes to designing and working with people."

Formed from the husk of previously announced but unfinished Ouroboros, The End Is Nigh let him really ponder if everything had been worth it. It's a story of perseverance by any means, challenging you to find the motivation to try again and again, without the promise of a happy ending. Thematically, it was his toughest undertaking, and he considers it one of the best games he's made.

Right now, McMillen is seeing where the wind takes him. Later this year there's Legend of Bum-bo, a Binding of Isaac prequel, and he mentions a desire to release smaller, weirder games in the future. After nearly quitting two years ago, now he sounds optimistic, no doubt bolstered by having Vinh around to riff ideas with and Ryder's site collecting together Isaac's ardent fans. But whatever comes next, he's resolute that the ending of Binding of Isaac has already happened.

"The Forgotten in itself is the final ending of the game. You loosely see that Isaac's bones have his soul chained to the ground because of how he died," he explains. "It puts into question what happened and why, and where is he now. In the story of the game, that is its conclusion, and I don't see myself adding any more to that."