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The past, present and future of The Binding of Isaac

With the final update released, is the creator ready to step away?

The Binding of Isaac was released seven years ago. Its last major update for the foreseeable future was just released, and Edmund McMillen, its creator, may be ready to walk away.

“It’s hard to be done with the game, but, as of right now …”

He pauses. It amounts to just a couple of seconds, but it feels longer. This is common. A designer sees monumental success from a single project, but after a few years, they pull themselves away from it. That success becomes a creative burden, poisoning everything else they work on.

McMillen continues.

“No, I’m never done.”

Originally designed in Flash, The Binding of Isaac has since been updated and released on around a dozen platforms, with millions of copies sold.

The basic premise: A boy named Isaac is locked in the basement of his home by his mother. There, he must survive an unending wave of horrors that are probably just representations of his own psychosis. The core gameplay, though, is fairly traditional. Really it’s just a shooter with original Zelda DNA mixed in.

The Binding of Isaac - bloody floor Edmund McMillen and Florian Himsl

And yet people have spent an astonishingly long amount of time playing it. A Steam review, written in April 2018 by user AmSnek, lists the reviewer’s play time at 1,572.6 hours. Almost all of the reviews listed are from people who have played for more than 100 hours. When The Binding of Isaac grabs you, it does so without mercy.

It’s this fanbase that has kept McMillen so engaged with the project. Over the last year he’s been working with his team on free updates to the latest version of the game, The Binding of Isaac: Afterbirth Plus. These updates were almost entirely conceived by The Binding of Isaac’s community, released as free mods and eventually added to the full version of the game for everyone to experience.

The idea for these updates, called Booster Packs, was simple: “What if people make really cool stuff and we can put it officially in the game? It would encourage people to make cooler stuff because there was a chance for it to be in the game,” McMillen said in an interview with Polygon.

The execution of this plan proved more complicated, though.

“There were definitely a bunch of issues that I hadn’t foreseen at all. I simply didn’t have a great technical understanding of how this would all go down,” he said. “And we only had one person, Adrian [Gavrilita], who was the lead programmer on Afterbirth Plus. So it ended up taking a lot longer than I thought.”

In addition to rebalancing some of the fan-made items, there was artwork to clean up and programming issues to work around. The first three Booster Packs were released over the course of four months in 2017, which was relatively on schedule.

For the fourth and fifth packs, McMillen enlisted a team of modders behind Antibirth, a popular fan mod that added dozens of new mechanics to Isaac.

Antibirth had come out, like, a month or two before Afterbirth Plus. I right away got in contact with Vinh, who was the lead designer and programmer for the whole project. He has such a great mind for Isaac-related things,” said McMillen.

These final two packs, the last of the Boosters for The Binding of Isaac, are ambitious and easily on par with traditional paid downloadable content. The most recent pack added an entirely new playable character, designed by McMillen. “I always wanted to include one item from me on each of these packs,” he explained.

In describing these packs, McMillen did sound like he was trying to atone for his lack of involvement in the initial release of Afterbirth Plus.

Afterbirth Plus was developed at a time where I wasn’t really available to develop,” he said. “It was a fucked-up situation. A lot of stuff in my personal life, I wasn’t able to be there and guide things as much as I wanted to. [...] I don’t want to say ‘right any wrongs,’ because I don’t think it was a complete disaster, but … I just wish I was there more.”

In a blog post in 2011, McMillen described his original plans for Isaac. He specifically called out having “70 special items,” “8 dungeons” and “42 enemy types.” At launch, there were six playable characters.

Today, with the latest Boosters, the total number of possible pick-ups in Isaac has surpassed 700, with 15 playable characters.

“It is designed in a way that allows for a hugely bloated amount of content,” said McMillen. “The more you go, though, the more dangerous things become. Because even though it’s organized chaos, you have to balance the chaos a little bit. You get into a situation where the shell that you initially built this thing in is falling apart, and you’re just taping it together.”


The chaos from all of the possible item combinations and gameplay implications is only part of what makes The Binding of Isaac a thrilling project for McMillen to work on.

The game’s story, mostly told through unvoiced cutscenes, between-level cinematics and other nontraditional means, continues to be a driving focus for McMillen.

Back in 2015, he launched an ARG that encouraged the community to work together to unlock a new character in the game. Using a mix of voicemails, missing-child flyers and coded messages designed to be uncovered by fans, McMillen was able to convey elements of the Isaac storyline in bizarre new ways. The ARG culminated with a gang of six Reddit users uncovering GPS coordinates and heading out to Santa Cruz, California. They were told by McMillen to “bring a shovel.” The end result was a buried statue of one of the game’s boss characters, Greed, which directed fans to a secret Twitter account that encouraged people to “give him a voice” by posting a message there. The game was then updated, adding a new playable character, The Keeper, to its roster.

“It wasn’t something I was being paid to do,” McMillen said of the ARG. “I wasn’t making money off of it, but I got to do it to interact with the community and utilize something that I made to expand it in a nontraditional way.”

The fifth Booster Pack’s largest secret, a new playable character named The Forgotten, is McMillen’s follow-up to the ARG.

Design document for a new character in The Binding of Isaac: The Forgotten
A design document for a new character in The Binding of Isaac: The Forgotten.
Edmund McMillen

The Forgotten is a skeletal version of Isaac who is able to switch between a physical, bony form and a ghostlike form that’s chained down.

“One day, I’d like to do a sequel to The Binding of Isaac,” he said. “There are certain elements of the game’s design that I would want to hold for a sequel. Because I don’t want to introduce whole new mechanics. I would have to rewrite the game; that would change everything.”

So rather than start from scratch, McMillen has been dropping pieces of what he’d view as a sequel into the core game. The Forgotten is one such example. McMillen describes it as “thematically more appropriate for a sequel.”

“I want to do some abstract storytelling with a character,” said McMillen. “Just some themes. I want the player to play as a skeletal character, whose soul is chained to it, and I want that to speak more than a cutscene. […] It was, like, a fun way to basically say, ‘Isaac’s body still exists and its soul can’t leave because it hasn’t been buried on hallowed ground. His soul is stuck.’ […] It opens a lot of different ways to tell the story, different pathways to go. That’s where I wanted to go in the future.

“The stages of decay — from Blue Baby to The Lost to The Keeper to The Forgotten — it’s all part of a story that I’m trying to tell through characters and themes. Where can I take this? Where do I want to go? How much more do I want to push, and how much do I want to save for something bigger in the future?”


But before he looks to the future of Isaac, McMillen is going to look into the past.

His next game is The Legend of Bum-bo, scheduled for release this year. Like most of McMillen’s stuff, it’s a bit bizarre. Bum-bo is a prequel, set before the events of The Binding of Isaac, but in the same universe. While familiar characters (like Bum-bo himself) appear, the gameplay is a major departure from that of Isaac.

“I’m sure that people who like Isaac will like Bum-bo,” explained McMillen, “but it’s a strategy game. It’s a totally different type of experience. It’s more relaxed and more of a thinker’s game than a run-and-gun type.”

The Legend of Bum-bo has more in common with Bejeweled than Smash TV, but with a layer of tactical combat mixed in with match-three mechanics. At one point, McMillen referenced “action points” in the game, saying that’s something players might connect to an RPG like Fallout.

At first glance, Bum-bo seems a lot sweeter and more child-friendly than much of McMillen’s work. His hand-drawn artwork is brought to life by his programmer, James Id, to create lively 3D worlds within the confines of a cardboard box.

“With James, the thing that we have in common — outside of movies and being weirdos — is that we had difficult childhoods,” McMillen said. “And it was appropriate to the story to explore elements that feel true to us. A lot of the stuff in Bum-bo is reminiscent of being poor but being a creative kid, so you had to utilize the stuff around you. Making cardboard spaceships. Cardboard boxes are a huge theme in almost all my games, and now it’s almost looped back in on itself, and it’s a game within a cardboard box.”

This theme of finding ways to conquer a tough situation is a through-line in most of McMillen’s work. “It’s a piece of me. It’s such an honest chunk of my life,” he said. “As an artist you just open up, and allow life and time to just inspire things. My best projects are like that. The End Is Nigh was like that. Shitty situation. How do I write about an awful situation, and how do I take that and turn it into something that can be enjoyed?”

“Art in general has always been very therapeutic and honest to me. I tried to write poetry as a teenager and it was, like, horrid — the most embarrassing shit you could imagine. And I found that over the years, I can write poetry through video games, and I can express myself in a way that people don’t get. And they don’t get enough to make it embarrassing, if that makes sense.”