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This is a research paper I wrote about The Binding of Isaac and other popular roguelikes currently finding popularity.

sebastian alberini, Blogger

December 9, 2014

32 Min Read

Sebastian Alberini

CTIN 190

Research Paper



The Rise of the Roguelike: Why The Binding of Isaac Makes for Great Stories


The Binding of Isaac is a game that was “designed to fail” according to its creator, Ed McMillen, and yet it has procured a massive cult following and sold over two million copies to date (McMillen, 2012). Even still, the number of copies sold is certainly climbing if the recent re-release entitled The Binding of Isaac: Rebirth is also accounted for, and the mere existence of an updated release is a testament to the success of the original game. Gamers appear to be enamored with McMillen’s “roguelike” effort; roguelikes are defined by their adherence to randomly-generated environments, perma-death, lack of a linear path, and (historically) turn-based gameplay (Hatfield, 2013), which apparently makes Isaac a “roguelike-like” due to its real-time action. Hyper-accurate nomenclature aside, McMillen claims that Isaac was made “to clash with mainstream games” by way of its unique focus on religious themes and niche target audience (fans of the old 2D Zelda games), and yet the IP is wildly successful and highly revered for its endless replayability, consistent feeling of discovery, and general aptitude toward the treatment of the roguelike genre, which has historically been enjoyed by a narrower, more hardcore audience (Hatfield, 2013). However, Isaac is not as much of an anomaly as its creator may initially imply, for other examples of highly successful roguelikes have appeared within the game industry in recent years, namely titles such as FTL:Faster Than Light and Spelunky, the latter of which actually preceded Isaac. Yet, the reemergence of this very particular, niche genre is no coincidence, for it is the parallel explosion of the Let’s Play online culture that has allowed for the booming popularity of games like Isaac which may have been a small-scale cult hit in their respective creator’s conception of the game. Specifically, the Youtube/twitch.tv culture has provided a platform on which gamers can not only discover new titles but express their own personal experiences and stories with other fans of the games they love - this sharing of experiences, however, would not take place without a fun, engaging, and compelling basis for gameplay, which is arguably the main appeal behind successful roguelikes. Isaac, specifically, authors its own take on the genre by combining previous conventions such as procedural dungeons and permanent death with more unique elements such as a finely-tuned difficulty curve that introduces new content with every playthrough and the ability to construct entirely new game rules with each new item attained. More importantly, Isaac and its successful roguelike counterparts utilize their dynamic elements to function as conducive platforms for one-of-a-kind stories for players; these platforms in-turn offer gamers an alternative to the strictly linear narrative structures that pervade the games industry.

Outside of the cult following largely facilitated by the Youtube/twitch.tv culture that surrounds Isaac, McMillen’s brainchild also receives positive critical feedback for simply being a great game, boasting an 84 Metascore on the original title and an 89 on the re-release(metacritic.com,2014). In other words, unlike certain media-based cult followings such as that of The Room(2003) or the more recent Sharknado(2013), the product that underlies Isaac’s mass-appeal is not an utterly terrible piece of work; game industry critics and the gamers themselves generally agree that TBOI offers fun and compelling gameplay, and the success of the game, both commercially and critically, contrasts with its relatively modest initial development time of three months. For those who have never experienced Isaac, its game loops consist mainly of traversing procedurally-generated, 2D dungeons whilst first projectiles at enemies in order to advance through the rooms, past the bosses, and to the eventual final battle with Mom. It is also important to note that Isaac features many roguelike elements such as permanent death and RPG elements like item collecting and stat building.   binding5.jpg

So what is it about this particular indie title that has such staying power and widespread appeal? According to the game’s creator, as cited in a self-written article titled Postmortem: McMillen and Himsl’s The Binding of Isaac, the game’s success is due in part to the properly executed roguelike design: “Once you crack the roguelike formula … 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.”(McMillen, 2012). Just to clarify, McMillen is not so narcissistic and audacious here as to claim that his particular game “cracked” the roguelike formula and is thus an “everlasting” design. He’s merely speaking to the strengths of the genre in its most ideal form, and goes on to speak about what went particularly well with Isaac’s handling of the roguelike:

“ … what made Isaac different than most roguelike games … 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.”

What McMillen is touching on here is an emphasis on “affective loops,” a concept nicely articulated in an article titled Experience-Driven Procedural Content Generation; essentially, affective loops draw upon physical and emotional interactions between the user and the system in order to facilitate real-time alterations and direct the user experience in a more deliberate way (Yannakakis, Togelius, 2011). And such is the power of procedurally-generated content - McMillen is able to trace the player’s interaction with the game world (in this case, the only knowable interactions are physical - i.e. the actual button inputs by the user - and the emotional pieces - i.e. current level of rage - are hidden information), and then proceed to alter the generation of new content accordingly. While the extent to which Isaac utilizes such concepts programmatically is unknown (save for a technical interview with the game’s programmer), it is clear that the game is able to exude a certain liveliness because of its usage of dynamic difficulty scaling and content generation. So, if the player has full health and is yet to have taken damage by the fourth floor, the game can include a couple of extra-difficult rooms on the next floor in order to keep things interesting. This is certainly speculation, but what is for sure is that a player’s input and general ascension toward a higher skill level will in-turn unlock more challenging content, thus engaging with the player in a feedback loop - the player succeeds at achieving a difficult task, and is treated with an expanded set of more difficult potential content that is fed into the content generation machine. So, for example, if a player finishes a certain floor named The Depths thirty times, they unlock a new, more difficult boss named Something Sticky whom may now appear as a boss at any point in the game from that point on (bindingofisaac.wikia.com,2014). And while this minor shift in the generation algorithm may seem insignificant at first, it is actually the combination of this “secret” and hundreds of others that are consistently ramping up the difficulty and introducing new concepts that add to the aforementioned liveliness both in the current playthrough but also in-between playthroughs.

However, liveliness is not only conveyed through the introduction of new bosses and levels, but also in the generation of items throughout each room. There is atleast one item to attain on each floor, and each boss drops a new item. (McMillen, 2014). These items range in effects from simply increasing attack range, such as Mom’s Lipstick, to allowing the player to direct extremely powerful missiles and obliterate most any room in a matter of seconds with Epic Fetus (bindingofisaac.wikia.com,2014). Both items are depicted below:

Mom’s Lipstick and Epic Fetus

Before and after Epic Fetus item


The wide array of items act as a massive staple in the gameplay throughout Isaac and largely constitute what Ian Bogost would refer to as the “procedures” that apply the “constraints that create possibility spaces, which can be explored through play.”(Bogost, 2008). These items essentially write rules on top of the very few given rules that McMillen provides, namely that you control a character and fire projectiles, are able to collect keys to open doors and attain new items, can use bombs to blow up rocks and other objects, and must defeat the bosses in order to proceed to the next level. If these constraints acted as the only procedures present in Isaac, we could assume that the end product (and included possibility space) would feel much less alive than it currently does. Moreover, McMillen opts to allow the wide array of potential item drops to constantly shift the possibility space mentioned by Bogost, essentially rewriting the entire script of rules at any given moment. So, if a player has collected the ability to shoot massive scythes at his enemies and lay toxic goo in his wake which slows down any approaching enemies, he may happen upon a D4, which rerolls the entire inventory of items, and the player is suddenly granted a pair of wings to fly over any obstacles and can additionally emit railgun-esque laser beams that increase in damage as the player takes hits from enemies (these are all real things that can happen in this game). The unadulterated consistency with which Isaac’s systems are willing to completely rewrite the game rules is a huge part of its allure; the ever-changing possibility space gives the impression of a breathing world, and keeps the simple mechanics of the twin-stick shooter feeling fresh and new with every run.

So, relating back to the affective loops article, here is a graph of a tried and true approach to procedurally-generated content:

       Experience-Driven Procedural Content Generation, 2011


With this technique, as it has commonly been applied to multiple forms of media including games, the designer is focused on perceiving the inputs of the player and in-turn crafting a desired “player experience model,” which will then inform decisions on how to adequately pump out new content that will better adhere to that player’s specific desired model. The “content quality” section is where Isaac truly vears off of this directed path and is thrust uncontrollably into a nearby lagoon (in a good way). That is to say, the generation of new items in upcoming rooms is at times the exact opposite of quality in terms of how it applies itself to some consistent, deliberate player experience; that is to say, the player will often come across an item that, if picked up, would completely destroy the chances at successfully completing that specific playthrough. A good example of one such item is the Cursed Eye, which can randomly teleport the player out of a room at any given moment, such as when you are on the verge of defeating an incredibly difficult boss... but must now restart that boss fight with significantly less health...(I’m not going to cite the wiki here because I learned this first-hand and it sucked - I am the citation (Alberini,2014)). Mind you, these items do not appear with a label telling you what they do - they are mere pixelated pieces of floating artwork - and new players will quickly learn that unknown items might be worth a quick Google search before being acquired through physical contact. Alternatively, an item might appear that makes completing the current playthrough relatively trivial, such as combining Polyphemus and Technology, which allows the player to blast away any enemy with a massive, overpowered laser beam that covers the entire screen. Most developers work tirelessly to eliminate such game-breaking occurrences, but Isaac welcomes these moments with open arms.


        Polyphemus + Technology = Extremely OP Laser Beam

    What I am getting at here is that the systems at play behind Isaac do not necessarily feel the need to dynamically generate content that will lend itself well to a prescribed player experience. Instead, through the implementation of a vast array of unique items with interesting synergistic effects and a seemingly unwieldy and unpredictable methodology for dispersing these items throughout the environment, McMillen has created a chaotic, ruthless, and altogether thrilling roller-coaster ride of possibility space. And while I would love to further nerd out over why the programming behind Isaac is so effective at conveying this lack of predictability in regards to the play space, I feel it is more important to note that it is exactly this feeling that promotes the other half of Isaac’s success, which is its prominent online presence as a socially shared experience through Youtube and twitch.tv.

Specifically, it is the wildly altered experience from playthrough to playthrough that allows Isaac to be a great game for crafting stories to tell your friends. The story here is not merely the narrative of Isaac’s plot, which would be the same every time: “Isaac’s mom attempts to kill him because God asked her to, but he manages to escape her grasp and became an evil demon in the process.” Okay, that’s a pretty wacky story that has its merits, but the narratives that are actually shared across channels such as Youtube or twitch are much more referential toward the specific items or bosses that a player came across. These types of narratives, which are acknowledged in Jesper Juul’s A Brief Note on Games and Narratives, are retellings of what specifically happened in a playthrough: “Games may spawn narratives that a player can use to tell others of what went on in a game session.”(Juul, 2001). Moreover, Juul also notes that as players all seek to “realise an ideal sequence of events,” namely blasting through enemies from room to room and eventually defeating Mom, they can opt to craft narratives based on the variable sequence of events that take place in reaching that common ideal. To exemplify this point in relation to Isaac, I spent some time on popular twitch.tv channels featuring the game, and absorbed some player stories:

“I pulled a tech2, number one, mulligan, and sad onion on a run just now… killed mom in 5 seconds with 12 trillion flies :D.” - Random twitch dude #1

“There was a guy on reddit that started an eden run with brimstone and the yellow cats head thing.” - Random twitch dude # 2

And at times, viewers will interject with a bit of wisdom:

“DONT kill the Lamb to fast. It can glitch out and become invicible!” - Bad grammar but knowledgeable twitch dude #3

    These condensed storylines function perfectly for twitch.tv chats and Youtube comments; they are short, to the point, and immediately understandable and intriguing to fans of the game and its systems. The length of each playthrough is also perfectly suited to these condensed narratives. A playthrough rarely takes more than an hour, meaning the likelihood of generating stories that are worthy of social sharing is heightened by the ability to play through multiple new adventures in a short period of time. But these twitch.tv and Youtube viewers are not there merely to share their story; there is entertainment value inherent in viewing a personality that you enjoy (such as that of a big Youtuber) crafting a story in realtime. Interestingly enough, it was the advent of these big Youtubers who recorded various Let’s Play videos for Isaac that may very well have caused the success of the game: McMillen notes that it was not until hundreds of new Isaac videos were uploaded daily to Youtube that the sales for the increased exponentially (McMillen, 20).



  More twitch.tv banter on a Binding of Isaac stream

    However, Binding of Isaac is not alone as a roguelike game that is prime for generating stories in the same way that it generates its room to room challenges. Other roguelikes such as Spelunky and FTL also held their own on twitch.tv against an increasing barrage of esports broadcasts for massively popular games like League of Legends or Counter Strike: Global Offensive (you will not see these games on the front page of twitch.tv today, however, they faired quite well around the time of their release). The success of these games is contingent on the fostering of passionate communities of gamers who crowd around what Katie Selen and Eric Zimmerman would refer to as “struggling together or in parallel” against an opposing “game system.” (Selen, Zimmerman, 2003). This very specific conflict between the player and a complex system, which within the context of roguelikes is generally very challenging and adheres to a more hardcore standard of trial and error, stimulates a sense of commensurability amongst the game’s participants. This parallel struggle is then shared across the ever-expansive media outlets in the form of interesting stories that each player experiences; these stories may not be presented in the same ways as Isaac given its unique pixelated art style and bold use of religious imagery, but unique instances of emergent narrative are possible in any ambitious rendition of the roguelike, whereby one-of-a-kind experiences and an overall sense of novelty in discovering new mechanics is awaiting in each new room generated. The recent success of roguelikes makes the genre an enticing new prospect for small development teams; developing a system that can populate entire worlds with self-maintaining narratives and inherent replayability is significantly less laborious than a hard-coded world with a hand-holding style narrative. Moreover, Isaac represents a fantastic venture away from the pre baked, linear, and often ephemeral narrative structures that are present in larger titles within the industry, and makes a solid case for the re emerging and further development of the roguelike genre within a more modern context.    



  1. McMillen, Ed. "Postmortem: McMillen and Himsl's The Binding of Isaac."Gamasutra Article. N.p., 28 Nov. 2012. Web. 6 Dec. 2014.

  2. Hatfield, Tom (2013-01-29). "Rise Of The Roguelikes: A Genre Evolves". Gamespy. Retrieved 2013-04-24.

  3. "Metacritic - Movie Reviews, TV Reviews, Game Reviews, and Music Reviews."Metacritic - Movie Reviews, TV Reviews, Game Reviews, and Music Reviews. N.p., n.d. Web. 07 Dec. 2014.

  4. Yannakakis, G.N.; Togelius, J., "Experience-Driven Procedural Content Generation," Affective Computing, IEEE Transactions on , vol.2, no.3, pp.147,161, July-Sept. 2011 doi: 10.1109/T-AFFC.2011.6

  5. "The Binding of Isaac Wiki." The Binding of Isaac Wiki. N.p., n.d. Web. 06 Dec. 2014.

  6. Bogost, Ian. “The Rhetoric of Video Games." The Ecology of Games: Connecting Youth, Games, and Learning. Edited by Katie Salen. The John D. and Catherine T. MacArthur Foundation Series on Digital Media and Learning. Cambridge, MA: The MIT Press, 2008. 117–140. doi: 10.1162/dmal.9780262693646.117

  7. Juul, Jesper. "Games Telling Stories?[1]." Games Studies 0101: Games Telling Stories? by Jesper Juul. N.p., 2001. Web. 6 Dec. 2014.

  8. Tekinbaş, Katie Salen., and Eric Zimmerman. Rules of Play: Game Design Fundamentals. Cambridge, MA: MIT, 2003. Print.

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