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Postmortem: McMillen and Himsl's The Binding of Isaac
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Postmortem: McMillen and Himsl's The Binding of Isaac

November 28, 2012 Article Start Page 1 of 4 Next

How did a game destined for failure become a cult smash? In an article originally written for Game Developer magazine, Edmund McMillen (Super Meat Boy) discusses how he added religion to The Legend of Zelda, mixed it with a roguelike, and came out with a surprise hit.

On paper, there is simply no reason for a game like The Binding of Isaac to have become as huge as it has. It makes no sense -- and this is coming from the person who believed in it the most. I knew Isaac was special, but if you asked me to bet on whether Isaac would sell over one million copies in less than a year, I would have bet against it.

You see, The Binding of Isaac was made to clash against mainstream games -- it was designed to be a niche hit at best. I had hoped it would gain some minor cult status in small circles, kind of like a midnight movie from the 1970s. From any mainstream marketing perspective, I designed Isaac to fail -- and that was my goal from the start.

When I started working on The Binding of Isaac, I was still haunted by the end of Super Meat Boy's development, and the hoops we had to jump through to get there. I wouldn't say Super Meat Boy was "selling out," but it was the closest I was going to come to it when it came to playing by the rules to make sure that we could sell the game that consumed two years of our lives (and all of our money).

After SMB, I no longer had those worries -- I could afford to take a bigger risk and fail, if I felt like failing. I wanted to make something risky and exciting now that the financial aspects of that risk were gone. And I wanted to really push my limits to get back to where I had come from -- a place where there were no boundaries, where I could create anything without worrying about making a profit.

The Binding of Isaac started in a weeklong game jam. Tommy Refenes (Super Meat Boy co-developer) was taking a vacation, so I decided to do the game jam with Florian Himsl, who programmed a few of my previous Flash games (Triachnid, Coil, and Cunt). Florian is the kind of guy who is up for anything; he wasn't worried about his reputation, and was basically down with whatever I wanted to do in terms of content. This was good, because I had two clear goals when I started designing Isaac: I wanted to make a roguelike game using the Legend of Zelda dungeon structure, and I wanted to make a game about my relationship with religion.

Both goals were challenging but very fun to design, and after seven days we had something that was turning into a game. It seemed too good to pass up, so we continued working on it in Flash (using ActionScript 2). At this point in the process, I wasn't thinking about how we were going to sell this game (or if we were going to be able to sell the game at all!); it was just a challenge we both wanted to finish.

We finished The Binding of Isaac after about three months of part-time development. We released it on Steam, and it was selling okay; for the first few weeks, the game was averaging about 100-200 copies a day, eventually stabilizing at about 150 a day after a few months. By this point, the game had already exceeded my expectations, but five months after release something very odd happened. Our daily average started to climb. 200 copies per day turned into 500 copies, then 1,000 copies, and by the seven-month mark Isaac was averaging sales of more than 1,500 copies a day and climbing. I couldn't explain it -- we hadn't put the game on sale or anything, so I was clueless as to why sales were continuing to grow.

Then I checked out YouTube, and I noticed that fans of the game were uploading Let's Play videos constantly -- over 100 videos every day, each getting tons of traffic. Isaac had found its fanbase, and that base was growing larger and larger. Not bad for a game that was meant to fail!

What Went Right

1. Roguelike Design

The roguelike formula is an amazing design plan that isn't used much, mostly because its traditional designs rely on alienatingly complicated user interfaces. Once you crack the roguelike formula, however, it becomes an increasingly beautiful, deep, and everlasting design that allows you to generate a seemingly dynamic experience for players, so that each time they play your game they're getting a totally new adventure.

I wanted to combine the roguelike formula with some kind of real-time experience, like Spelunky, but I also wanted to experiment more with the traditional role-playing game aspect of roguelike games Crawl and Diablo. Fortunately, using the basic Legend of Zelda dungeon structure as the game's skeleton made it easy to rework almost all the elements of a traditional roguelike formula (procedurally generated dungeons, permadeath, and so on) into a real-time dungeon crawler format. Almost every aspect of the game seemed to fall perfectly into place with little effort.

Let's start by looking at the Legend of Zelda dungeon and resource structure -- it's simple, and really solid. Keys, bombs, coins, and hearts are dropped in various rooms in the dungeon, and the player needs to collect and use these resources to progress through each level. In Isaac, these elements were randomly distributed and not required to progress, but I included them to add structure to the experience.

I also pulled a lot from Zelda's "leveling structure," where each dungeon would yield an item as well as a container heart to level up the character and give the player a sense of growth; in Isaac, each level contains at least one item, and the player can get one stat-raising item by beating the boss. These items are random, but still designed in a way that made it so your character would have some kind of physical growth as you progress through the game.

I approached the roguelike design from many different directions with Isaac, but at its core, what made Isaac different than most roguelike games (well, aside from its visuals) was how I dealt with the difficulty curve. Instead of using traditional difficulty settings, I simply made the game adjust to players as they played, adding increasingly difficult content to the game as they progressed. This made Isaac feel longer, richer, and gave it the appearance of a story that writes itself. Using this design also allowed me to reward the player for playing and playing well, with more items that would help aid in their adventures and keep the gameplay fresh and exciting.

Once the player finally overcomes Mom, they usually assume the game is over, but instead get a new final chapter, six new bosses, a new final boss, and new items that shuffle into the mix. When the player beats the final chapter, they unlock new playable characters and items, and when they beat the chapter with each new character, they'll unlock even more content that makes the game even deeper still.

With Isaac, my goal was to create "magic." I wanted players to feel like the game was endless and alive, that the game had a mind of its own and was writing itself as they played. I remember the original Zelda having this feeling of magic and mystery. You weren't sure what things did until you experimented with them, and you had to brainstorm with your friends and put all your findings together in order to progress. I felt like since I was referencing Zelda so much in Isaac's core design, I should also complement it with the feeling of mystery I felt it had back in the day.

Article Start Page 1 of 4 Next

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Michael Griffin
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I really love this game; Isaac's story reminded me of improvising a D&D campaign using the bits and pieces of toys I had on me--albeit in a darker way. There's a sadness to this game that really adds another dimension, which is why it can sometimes be hard to play for too long.

A Wii U or 3DS version would be fantastic--local co-op crossplay between them would be even better. I think the GamePad is particularly well-suited to single-screen play here, too. I didn't know Nicalis was working on the new version! That's great news.

Thanks for this post-mortem. I think it's refreshing to hear stories where the creative process is allowed room to fail--and soars because of it.

Sean Hogan
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Rad, glad it worked out so well! In general I wish people made their games more personal and as reflections of themselves...there's something about games with parts of the personalities and thoughts of the creators that's appealing - maybe gaining insight into their minds, etc. Are you going to be making all of the 16-bit graphics for the console version?

Michael Pianta
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Great article. I hope Nintendo does allow this game on the Wii-U. I think it could be a perfect fit - you could pull it down onto the game pad or whatever. And also I just want Nintendo to stay relevant. Indie developers like you are the bright future of games, all the consoles need to have this sort of thing on their platform.

Michal Dawidowicz
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Hey, you can make Flash games outside of FLA for years now, doing a little bit of research would probably saved you tens or hundreds of hours fighting with big ass FLAs. But past aside, I'm patiently waiting for the Rebirth now!

Tinus TheBoss
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So is the Rebirth not coming for pc/ steam? only for console? :S

Matt Hackett
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Many of the limitations you faced sound just like the issues I'm having with HTML5, which currently feels like developing with an old, shitty version of Flash.

I read this like three times in GD Mag. Solid game, great take-aways. Thanks for writing this, loved it.

Brian Devins
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I had no intention of buying this game until my friends, one after one, gushed over it. I bought it and couldn't believe how riveting it was. It's actually one of my favourite games of all time. I sure hope Reborn will make it to PC - I feel like I haven't paid enough for this game yet.

Craig Timpany
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I wonder if the Binding of Isaac could've made it through the Steam Greenlight process if it were pitched today? I'm not sure they'd even allow it to have a listing, seeing as they disallow "inappropriate or offensive content," whatever that means.

Daniel Boutros
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A great game. One my favorites of the year, pre-Wrath of Lamb. After that, it felt like starting again for me. :)

Was stunned it didn't even get an award nomination at any of the indie shows. Smelled like bullshit to be honest.

BTW Tyrone, I'm jealous. Great game dude.

Epona Schweer
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Reason #437 of why I work with indie creatives and am such a fan of McMillen's stuff.

Andreas Ahlborn
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I`m left quite speechless, how much technical naivety the "what-went-wrong-paragraphs" 3 and 4 show. How comes that an obviously talented game designer like McMillen would eventually blame his tools for the technical problems he created by not knowing the basics about his crafting tools?
It`s like a carpenter would complain about his hammer, saying: a hammer is probably the wrong tool for driving in nails, because wood is softer than metal. FYI: You don`t hold a hammer by its head.
If Ankama can use flash to drive a game like dofus, and you have problems with it even if your scope is much smaller...that doesn`t exactly speak for you having done your homework.

Andreas Ahlborn
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Actionscript 3 hit the market in 2006. You should think every programmer that wants to use this technology would have made the shift long ago.

Samuel Roberts
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Florian Himsl was the programmer, not McMillen, and AS2 was chosen because that was what Himsl was comfortable programming in. Still seems somewhat off that someone would actively choose to continue using such outdated technology when AS3 has been around for over five years, but that was the situation.

John Jenks
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Congratulations on such an unexpected hit.

I loved Isaac. As much as it caught you off-guard with its success, it caught me off guard with its unique charm and its simple yet addictive gameplay. And the fact that you made this game for YOU and not for US... well that simply earns more respect for you and for the game from me.

Nikolay Osokin
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In regards to Negative Point 2 (Lack of testing) I wonder how McMillen would feel about conducting future business using the pay-for-the-alpha model that a few indies have adopted. That way no one's getting hurt that doesn't want to participate in a buggy alpha/beta period, and there's greater community interaction and gauging of interest, which would have shown him how 'tiny' his niche base would have been.

In general, Binding of Isaac has been a genius product since launch. I've put in 100+ hours (like most have, I presume) and am excited to give it a try on consoles, especially considering the complete overhaul of everything. I dig the flash graphics and design, but I generally would love a remixed version of most games, and the 4 options put on his tumblr all look neat.

Mohamed Almonajed
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God bless you Edmund.

jicking bebiro
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for me this is the best roguelike game i've ever played. This is what i call indie for being what it is .

Kyle McBain
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Never played but the basic structure, or should I say lack there of, sounds like Oblivion from the Elder Scrolls series. The items are not required to progress, and all the enemies level up as you do. It makes me wonder why I am leveling up at all. It's not "magic". It's laziness. And the fact that the map is exactly like Zelda is odd to me. I know it is not... but definitely feels like plagiarism. The only reason this game sold well is because of Super Meat Boy.