The Binding of Isaac (video game)

• 1. Introduction

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  The Binding of Isaac is a 2011 roguelike action-adventure game from independent designers Edmund McMillen and Florian Himsl. It reached Steam in September 2011 with almost no fanfare, and McMillen expected it to sell only a few hundred copies. Its hero is a crying child who flees his own mother into a monster-filled basement. A few years later it was being credited with reviving an entire genre.

  How did a small game built in Adobe Flash, about a mother who believes God wants her son dead, find such a large audience? What personal history pushed McMillen toward a story this dark? And why did Nintendo, after an early approach about a handheld version, turn the game down over its religious content?

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• 2. A Boy and a Trapdoor

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  The game begins in a small house on a hill, where Isaac and his mother keep to themselves. Isaac draws pictures and plays with his toys. His mother spends her days watching Christian broadcasts on television. The plot is only loosely based on the Biblical story that gives the game its name.

  Then "a voice from above" speaks to her, and she believes it belongs to God. It declares that Isaac is "corrupted with sin and needs to be saved." She agrees to remove every evil from his life, so his toys, his drawings and even his clothes are taken away. A second message tells her to cut him off from all that is evil in the world. She locks him in his room. The third time, the voice says she has done well but still doubts her devotion, and it tells her to sacrifice her son.

  She takes a butcher's knife from the kitchen and heads for his door. Isaac watches through a wide crack and begins to panic. He finds a trapdoor under his rug and drops through it just as she bursts in. Every run of the game is assumed to start at that moment.

  After the drop, the story offers little. The original game has 13 possible endings, one after each major boss fight. The first ten mostly introduce unlocked items and mechanics. The last three hold real clues to what the story means, though the full picture does not arrive until a new game and three expansions later.

  Between floors, cutscenes show Isaac curled into a ball and crying on two of the levels. His thoughts appear on screen. They range from rejection by his mother and humiliation from his peers to a scenario involving his own death.

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• 3. Dungeons of Tears

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  Each floor of Isaac's basement is built from ten to twenty rooms, chosen from a library of 200 pre-built layouts. McMillen then fills them with monsters and items and adds fixed rooms that every floor needs, such as a boss room and a treasure room. The result is a procedurally generated dungeon in the roguelike tradition, presented in top-down view with two-dimensional sprites.

  Combat borrows from the twin-stick shooter. Isaac fires his own tears as bullets, and he carries a limited supply of bombs that can damage enemies and clear parts of a room. McMillen compares the controls to those of the arcade game Smash TV. Characters differ in speed, health, damage and other attributes.

  Power-ups change everything. Passive items improve attributes automatically. Active items work once and then recharge as the player clears more rooms. Pills and Tarot cards are used up on a single effect, such as restoring full health. One item might let tears be charged by holding a button, and another might fire tears backward. Their effects stack, so lucky players can stumble into powerful combinations.

  A cleared room stays clear, so players can retrace their steps within a floor, but they can never go back once they descend. Money buys items from shopkeepers, and keys open treasure rooms. Health is counted in hearts, and losing them all means permadeath and a fresh dungeon.

  The descent has a clear shape. On the sixth of eight floors, Isaac fights his mother, then crawls into her womb. The eighth floor ends with a fight against her heart. An optional ninth floor, Sheol, holds the boss Satan. Winning with certain characters or under certain conditions unlocks items and playable characters, and the menus keep a record of every item found.

  McMillen drew the structure from The Legend of Zelda. In a typical Zelda dungeon, he observed, the player picks up an item that opens the way forward. He made sure every level of Isaac held at least one item, plus a bonus item for beating the boss. He also wanted players to learn by experimenting, as Shigeru Miyamoto had encouraged in the original Zelda. Four of the selectable characters follow the main classes of Dungeons & Dragons: fighter, thief, cleric and wizard.

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• 4. Two Kinds of Faith

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  McMillen grew up among relatives who were split between Catholic and born-again Christian beliefs. Both groups drew on the same Bible, yet their attitudes differed sharply. He found some Catholic rituals inspiring. Other beliefs in the family condemned things he enjoyed, including Dungeons & Dragons. From that contrast he built Isaac's story, in which religion can plant harmful feelings and also feed a dark kind of creativity.

  Another influence came from the 1980s, when the Christian right warned against heavy metal and video games. McMillen recalled that many propaganda films of the period featured satanic cults sacrificing children. He noticed that numerous Biblical stories echoed the same idea, and he built the plot around that overlap.

  He also liked what he called "really weird stuff," including toilet humor and other off-color jokes that never sat well with his family. He had explored that taste in games before Super Meat Boy. That earlier game made his name and even put him among the featured developers of Indie Game: The Movie. By his own account, though, Super Meat Boy was a "safe" game for someone with his sense of humor.

  Its strong sales changed the math. He no longer needed to worry about money, so he could take a risk. He saw Isaac as something that could easily be "career suicide" but would say what he really wanted to do.

  The timing helped. McMillen had planned to make Mewgenics next with Tommy Refenes, his Super Meat Boy co-developer, but Refenes was taking time off. McMillen wanted a low-stress project with modest expectations, and a Flash game fit the description.

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• 5. Flash, Steam, and Sound

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  Within a single week of game-jam work, McMillen and Himsl had a playable game written in ActionScript 2, the programming language of Adobe Flash. They agreed to finish it for release on Steam, with no expectation of big sales. Going from prototype to finished game took about three months of part-time work. McMillen also saw that procedural generation, as used in Spelunky and Desktop Dungeons, could teach him skills for Mewgenics.

  Danny Baranowsky, who had composed for McMillen on Super Meat Boy, joined shortly after the first prototype. The two traded work back and forth. McMillen sent artwork, Baranowsky wrote themes in response, and the music often pushed McMillen to draw more. Baranowsky liked that beneath the dark tone lay silly undertones, so the game could not be taken too seriously. Some songs started from classical choral music and were bent to fit the theme. Boss tracks took cues from the work of Nobuo Uematsu on Final Fantasy. With time to spare, Baranowsky also wrote short pieces for shops and secret rooms.

  The tools fought back. ActionScript 2 was badly outdated and caused slowdown even on high-end PCs. It had no controller support, so Refenes wrote a program that let players unlock Steam achievements. McMillen later said he would not have used Flash at all had he known anyone would care about the game.

  Because sales were not a worry, the pair worked with Valve and avoided both censorship fears and the need for an ESRB rating. Steam also allowed frequent updates after launch, which console platforms could not offer without major cost. There was little outside testing, since checking every combination of items would have taken several hundred testers. McMillen accepted that buyers would serve as the playtesters.

  A week after the Steam launch, a demo appeared on the website Newgrounds. Merge Games produced a physical edition for United Kingdom stores in 2012, with the game, its soundtrack and a poster. After Adobe Flash Player was discontinued in late 2020, emulators based on WebAssembly, such as Ruffle, kept the original demo running in modern browsers on sites including Newgrounds and CrazyGames.

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• 6. The 3DS Refusal

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  In January 2012, with sales past 450,000 units, a publisher asked McMillen about bringing the game to the Nintendo 3DS through the eShop. He had doubts, given Nintendo's reputation for avoiding risque content. In late February he announced that Nintendo had turned the game down over "questionable religious content."

  He suspected the cause was Germany. Its classification board had rated the Windows version "age 16+" for potentially blasphemous content, the first time the country had rated a game that way. Nintendo executives had told him earlier that some blasphemy would be acceptable and that overtly religious material worried them more. He was asked whether he would make changes for the 3DS, but nobody gave him a list of what to change.

  McMillen guessed at Nintendo's motive. Because the game resembled The Legend of Zelda, an unsuspecting child might download it and be shocked, and that would reflect badly on the company.

  Several game websites were outraged. McMillen was disappointed but did not treat the loss as a major blow. Coverage of the news even brought a brief burst of sales on Steam, and he praised the platform for letting games publish without an ESRB rating.

  The story reversed in 2015, when Nintendo allowed the remake, Rebirth, onto both the New Nintendo 3DS and the Wii U. Three Nintendo staff championed the game: Steve Singer, vice president of licensing, Mark Griffin, a senior manager in licensing, and Dan Adelman, head of indie development.

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• 7. Wrath, Rebirth, and Beyond

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  On the 28th of May 2012, the expansion Wrath of the Lamb arrived on Steam. McMillen had a personal reason to make it. His wife Danielle had completed the whole base game, the first of his games to hold her interest. The expansion added 70% more content, including more than 10 bosses, over 100 items, over 40 unlocks, two extra endings and two extra optional levels. New alternate floors could replace the normal ones, with harder enemies and a different set of bosses. Trinkets, a new item type with passive or triggered effects, joined new room types. McMillen wanted a second expansion, but Flash had reached its limits. In May 2015, Himsl released a final Eternal Edition update for the Flash version, which added an Eternal difficulty mode and rebalanced several items.

  The way past Flash came from Tyrone Rodriguez of Nicalis, who approached McMillen in 2012 about bringing the game to consoles. McMillen agreed on conditions. The game had to be reprogrammed, include Wrath of the Lamb and the planned second expansion, and swap vector-based Flash art for 16-bit graphics. He also refused to handle any business matters, remembering how hard that had been on Super Meat Boy. Nicalis accepted.

  The Binding of Isaac: Rebirth launched on the 4th of November 2014 for Windows, OS X, Linux, PlayStation 4 and PlayStation Vita. Versions for Wii U, New Nintendo 3DS and Xbox One followed on the 23rd of July 2015. It added new characters, items, enemies, bosses, challenges and room layouts, and it is commonly cited as one of the best roguelike games of all time.

  Three further updates followed. Afterbirth, from October 2015, brought alternate chapters, characters, items and a wave-based Greed mode. Afterbirth+ arrived on the 3rd of January 2017 with more content and support for user-made mods. Repentance, released on the 31st of March 2021, folded in most of Antibirth, one of the biggest fan-made expansions. It added a new alternate path through the whole game, character variations and new final bosses.

  The world around Isaac kept growing. McMillen worked with James Id on The Legend of Bum-bo, a prequel released on the 12th of November 2019 for Windows and later for iOS and Switch. Isaac and Gish both appear in it. In 2018 McMillen announced a card game, The Binding of Isaac: Four Souls, made with Studio 71. Isaac has also become a playable fighter in Blade Strangers and a character in Crystal Crisis.

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• 8. Reviews and Reach

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  On Metacritic, the game averages 84 out of 100 across 30 reviews. Critics kept coming back to replayability. John Teti of Eurogamer called it "the most accessible exploration of the roguelike idea" he had seen. Edge described "an imaginative and quick-witted arcade experience that manages to be both depraved and strangely sweet by turn." Maxwell McGee of GameSpot said that "what remains is a tightly focused game that continues to feel fresh even after multiple completions."

  Reviewers also found the game hard, often because of the luck of the power-ups in a given run. The A.V. Club gave it an A and said it demanded "masochistic patience in the face of terrible odds." The huge pool of items eased that difficulty, though most only appear after many replays. McGee pointed out that the item menu lists what players have found without explaining what each item does.

  Opinions on its rough edges varied. Adam Biessener of Game Informer noted bugs at launch but wrote that "McMillen's vision shines through." Neilie Johnson of IGN warned that some players might be put off by the crudeness, yet called the game "totally random, highly creative and brutally unforgiving." Nathan Muenier of GameSpy found the shock value something to work past, then called the game "imaginative" and "utterly absorbing." Jordan Devore of Destructoid counted the visual style among its "biggest selling points." Kirk Hamilton of Kotaku heard a mix of Danny Elfman, Muse and Final Fantasy that added up to something "dark and unique." The game was nominated for Best Independent Game at the 2011 Spike Video Game Awards and lost to Minecraft.

  Sales started slowly, then jumped. McMillen credited the surge to many Let's Play videos in which players showed the game off. The attention also drew players who wanted to build mods, which shaped how the sequel handled modding. By November 2012 the game had passed one million copies, and at least a quarter of those buyers had also bought Wrath of the Lamb. In July 2014 McMillen reported over 3 million. After Rebirth, the combined games passed 5 million by July 2015.

  The game is also said to have helped drive growth in roguelikes since around 2010. Its success cleared the way for later games built on the same formula, including FTL: Faster Than Light and Don't Starve.

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