Sunday, April 29, 2012

Loops and Arcs

Here are two tools I've been using lately to better understand the functionality of my game designs.  The first is the loop, a structure that should be very familiar to those who have looked into skill atoms.  The second is the arc.


The 'game' aspect of this beast we call a computer game always involves 'loops'.
  • The player starts with a mental model that prompts them to...
  • Apply an action to...
  • The game system and in return...
  • Receives feedback that...
  • Updates their mental model and starts the loop all over again.  Or kicks off a new loop. 
These loops are fractal and occur at multiple levels and frequencies throughout a game. They are almost always exercised multiple times, either within a game or by playing the game multiple times.

Nested, dependent loops yields complex feedback loops and unexpected dynamics.  Loops tend to deliver value through the act of being exercised.  Thus they are well suited for mastery tasks that involve trial and error or repeated exposure. The goal of both loops and arcs is to update the player's mental model, however loops tend to rely on a balance of the following:
  • Interrelated actions that trigger multiple loops in order to bring about specific system dynamics.
  • Systems of crisply defined cause and effect that yield self contained systems of meaning.
  • Functional feedback that helps players understand causation. 
Loops are very good at building 'wisdom', a holistic understanding of a complex system.  The player ends up with a mental model that contains a thousand branches, successes, failures and nuances that lets them approach new situations with confidence.


'Arcs' have similar elements to a loop, but are not built for repeated usage. The player still starts with a mental model, they apply an action to a system and receive feedback. This arc of interaction could be reading a book or watching a movie. However, the mental model that is updated rarely results in the player returning to the same interaction. The movie is watched. The book consumed. An arc is a broken loop you exit immediately.

Arcs are well suited for delivering a payload of pre-processed information.  You'll typically find many arcs have the following footprint:
  • Simple independent actions such as turning a page or watching a movie
  • Simple systems that rely heavily on complex mental models to have meaning.  Text on a page is a good example. 
  • Complex evocative feedback that links together existing mental models in some unique, interesting or useful manner.  For arcs, the feedback is 99% of the payload and the actions and systems are simply a means to an end.  Once this payload is fully delivered, the value of repeated exposure to the arc drops substantially. 
Arcs are highly efficient at communicating 'success stories', a singular path through a system that someone else previously explored. The best teach a lesson, either informative, positive or negative. This is a brilliant learning shortcut but the acquired knowledge is often quite different and less robust in the face of change than 'wisdom'. With a slight shift in context, the learning becomes no longer directly applicable. It is not an accident that we make the distinction between 'book learning' and 'life experience'.

One of the common issues with arcs is that people burn out on them rapidly, rarely desiring to experience them more than once. It is possible to give arcs a bit more staying power by stringing them together serially in a sequence of arcs. This is a pretty proven technique and is at the base of the majority of commercial attempts to give content arcs longer retention.  Businesses that rely on a constant sequence of arcs to bring in ongoing revenue often find themselves running along the content treadmill.  If you stop producing content, the business fails.

Any loop can be superficially described as a series of arcs with one arc for each pass you make through the loop. This is an expanded loop. This is useful for recording a particular play-through, however it tells you little about the possibility space described by the loops.  Where loops often describe a statistical spectrum of outcomes, the arc notation describes only a single sample.

Mixing Loops and Arcs

Since both loops and arcs can be easily nested and connected to one another, in practice you end up with chemistry-like mixtures of the two that can get a bit messy to tease apart.  The simplest method of analysis is to ask "What repeats and what does not?"

Narrative games are the most common example of mixing loops and arcs.  A simple combination might involve layering a segment where the player is engaged with loops with a segments of arcs.  This is your typical cutscene-gameplay-cutescene sandwich.

However, the analysis can get far more detailed.  For example:
  • Parallel Arcs: You can treat the emotional payload of song as an arc that plays in parallel to the looping gameplay.
  • Levels:  The spatial arc of navigating a level provides context for exploring variations on a central gameplay loop. The 'Golden Path' in a single player level is really just another name for an arc. 
  • Micro Parallel Arcs:  A game like Half Life combines both levels and parallel arcs to deliver snippets of evocative stimuli as you progress through the level. 
These structures also exist in traditional media. For example, if you look at a traditionally arc-based form such as a book, you find an odd outlier in the form of the Bible.  At one level of analysis it can be seen as a story arc that you read through and finish.  However, it is embedded in a much larger set of loops we casually refer to as a religion. The game-like loops include everything from worship rituals to the mining of the Bible in order to synthesize weekly sermons.  The arc is a central rule book for a larger game consisting primarily of loops.

In the past I've discussed criticism as a game that attempts to revisit an arc repeatedly and embellish it with additional meaning.  The game is to generate essays superficially based on some piece of existing art.  In turn, other players generate additional essays based off the first essays.  This acts as both a referee mechanism and judge.  Score is accumulated via reference counts and by rising through an organization hierarchy.  It is a deliciously political game of wit that is both impenetrable to outsiders and nearly independent of the actual source arcs.  Here creating an arc becomes a move in the larger game. Intriguingly, tabletop roleplaying games use a similar core structure though the high level rewards differ.

Even in these complex cases, understanding which behavior is a loop and which is an arc helps tease apart the systemic behaviors. Of the two, loops are rarely discussed in any logical fashion.  People note the arcs and comment on them at length while being quite blind to the loops driving the outcomes. Both criticism and religions are lovely examples of how loop analysis can provide a practical description of the game's ruleset and magic circle even when the actual players are only vaguely aware of their constraints.

The growth of arcs in games

In the pre-computer era, games dealt almost entirely with loops.  The light arcs that games like Chess or Monopoly contained served the highly functional purpose of triggering a player's mental schema.  Once that setup payload was delivered, the games focused almost entirely on loops. One could easily claim that historically the term 'game' was used to describe an entertainment made predominantly of loops.

With the advent of computer games, designers started mixing more arcs with their loops. Adventure games, game endings and other narrative elements became more prevalent.  There are strong cultural and economic reason why this occurred at this period of time that are not strictly an inherent function of the computer game medium.

The primary driver for the proliferation of arc-based games is that they fit nicely into the existing retail business model.  Over the past 40-years, the dominant way you made money off media was to sell the customer an arc, be it a book, an album or a movie.  Once they had consumed that, you sold them another one.  With a large enough portfolio of games (typically managed by a publisher), you'd get a reliable stream of revenue.

As is the case with evolutionary systems, certain ill-fitting forms of games were punished financially and thus faded from the market. Assume you tried to build a popular evergreen game. You sell it once and that is the only money you get for the rest of the consumer's life. The retailers didn't want that outcome. Nor did the publishers. They preferred to sell players multiple games a year, year after year. The developers that made games that fit the constraints of this specific market reality flourished with profits from mega hits used to fund future moon launches.  Many of the modern game tropes such as beatable games, sequels, game concept conveyable by box covers, etc are a direct result this early retail environment.

Again, this is a statistical process, not a conspiracy.  Mammals and dinosaurs coexisted for millions of year but the shifting climate ended up being more amendable to one form than the other.  During the retail era, evergreen games still existed, but in diminished quantities.

Since systems are hard to understand, one popular just-so story that emerged during this period that arc-heavy games are some ideal outcome of new computer technology. This matured into a strange arc-worshipping segment of the population that predicts a technology-driven singularity for games that involves ever richer payloads and an eventual acceptance as an equal of other arc-centric media. Someone like David Cage, maker of Heavy Rain, is a modern example of such ideals.  But the roots go back much further to the dreams of early science fiction writers and researchers that had little practical experience with creating games.  They sold us a delightful dream for the future of games without understanding the first thing about the actual loop-like nature of games.

On reflection, it seems quite false to claim computers enabled arc-heavy gaming. A choose-your-own adventure was technologically feasible a hundred years ago. This suggests that arc-heavy games are not nearly as inevitable as some might imagine.

Consider the arcade market with its very different business requirements.  The arcade owners, publishers and developers were less interested in selling consumable boxes and more interested in repeat play.  This business constraint encouraged the creation of evergreen loop-based games that thrived for decades. The market and the culture hugely shapes the form of the games we make. It is certainly not locked in stone.

The market is shifting once again.  With in-app purchases, there is a large financial benefit to keeping the player engaged both emotionally and financially for long periods of time.  A fit game is one that you play forever all while paying for your hobby.  It is not one you beat and cast aside. This suggests that loop-heavy games may be making a comeback.

Untangling loops and arcs in existing game forms

So how do we evolve our designs with the market environment?  One exercise I've been performing on various games is identifying loop and arcs in a popular genre and then removing the arcs to see if what is left stands on its own.  What I've discovered is that arcs are almost never critical game elements. You can remove them and still have a playable game.

As an exercise, take your favorite genre (such as platform games) and remove the following:
  • Puzzles
  • Missions
  • Narrative sequences that are not specifically functional feedback that powers the completion of a loop.
To take this one step further, remove any elements of a computer game that you can 'beat' or that render the game boring or meaningless upon repeated play.

Can you make a wonderful game out of the remaining bones?  The vast majority of the time you can.  Even deeply arc-heavy graphical adventure games yield procedural hidden object games at their root.  Now, you can never get rid of arcs completely, nor would you want to.  Loops and arcs are ingredients and the goal is to create a new recipe with different mix rather than unquestioningly recreated the same meal again and again.

A brilliant future for loops

However, this is admittedly a rather reductive exercise.  What I'm far more interested in is what happens when we, as designers and developers, invest our full energy in exploring the potential of loops.  The language here is far less developed and it is an extremely fertile field for a young developer to make their mark.  Consider the following sparely settled frontiers:
  • Both Will Wright and Notch made millions by exploring the loops of player expression.  
  • Eve forges forth into new territory with every update by exploring the loops of economics and politics.  
  • Star Craft thrives because it taps into the mastery loops at the competitive heart of sports.  
  • No one is even talking about the loops inherent in religion, a system that has driven the behavior of humanity for thousands of years. 
  • Games of improv or bluffing or charades are all loop-based activities with nearly zero traction in the markets today.  These are games that can be played for life. 


Look for loops and arcs in your game.  What is the balance between the two elements in your design?  What does your game need?

This isn't a black and white situation and I respectfully ask you to avoid couching this in any tired us vs them terminology.  There is not one market.  You may find that the traditional arc-heavy recipes are exactly what you need.  If you are selling to a community whose norms for buying games were set during the retail era, creating a great beatable payload of entertainment may make you a lot of money.   Many of the popular indie sales channels remain conservative recreations of markets past.  It is a well trodden path.
  • Author evocative arcs
  • Build sequels 
  • Reduce portfolio risk in order to survive long droughts between mega hits 
If you are making a more modern evergreen game, consider how loops may result in delivering long term value to the players.  Question the forms of a traditional game and ask yourself if they are still valid in today's market.
  • Invent dynamic loops
  • Build a hobby
  • Create a fortified island nation with an ongoing stream of revenue
This is admittedly the harder path.  You need to analyze your design preconceptions. You need to understand the psychological functionality of what you are building something instead of merely mimicking patterns of the last generation.  Break your game down into loops and arcs.  Understand what is filler.  Understand what core elements form a endless engine for generating value (be it 'fun' or your outcome of choice.)

Above all, evolve.

take care,


  1. Hey Danc. I wrote a long response, and your blog horked on the length (probably rightfully). So I posted it on my blog instead. There she is:

  2. What I find most fascinating about this article is that I came up with a concept using the exact same terms, about a year ago.

    However I didn't apply a strict terminology or sequence as to what occurred inside an arc or loop - that was the "player's mental vocabulary." (as opposed to the game's internal vocabulary) What the model represented was still essentially "what the player thought about" but the content of thought was unlimited - in Pac-Man, for example, it could be the movement of the ghosts, the movement of Pac-Man, the state of the board, and the "eaten power pill" state, and the intersections of these various loops was how the player perceived gameplay. (An arc, as in your model, presented a one-way path.) A key assumption was that the player was most able to focus attention on just one intersection at a time, and awareness of all intersections was part of skill mastery.

    Increasingly I've dropped the loop model in favor of simply developing concrete vocabulary for the game; if something happens, I have to be able to describe it in terms apart from the mechanical content, as that forms the basis of communication to the player. What I discovered when I modelled purely in loops was that it was too easy to create ideas of excessive scope - games with massive, yawning loops for broad concepts like "build," "explore," "battle," "share" etc. that imposed mighty technical requirements and never achieved focus. It seems better suited as a shaping construct for after the basic play vocabulary is conceived and a successful prototype has been made.

  3. This was a good post, but I want to pick a nit. You say no one talks about how religion is a loop. In fact, one of the most prominent theories of "loop learning" is called "hermeneutics" and it began from Biblical scholars who wanted to explain the loops involved in understanding and translating scripture. A good introduction is Ron Bontekoe's Dimensions of the Hermeneutic Circle.

  4. What you refer to as loops is essentially a map of arcs. That said, if arcs can be "consumed", so can loops be "consumed". All the talk about how consumption is bad is just plain ridiculous because all art is consumed. No art is infinite.

    The real difference lies in that some games are made out of huge map of problems and others aren't, and so, some are easier to consume and some are harder. But still, few consume their games (incl. sports and board games) fully.

    You also seem to confuse two different concepts - that of a problem and that of an analysis.

    Reading books is not a problem. Yes, people turn pages and yes turning pages can sometimes be a problem (one you can solve by licking your finger), but so can everything else in the world. The real trick here is hidden in what's being enjoyed, and, in the case of books, it is the analysis that's being entertaining. If there are actions to be used with these sorts of entertaintment, then they are merely there for functional reasons.

    With problem solving, beside analysis, there is decision making, making actions much more important. Actions aren't just functionally important, they are also valued differently.

    Now let's get back to ARCS and LOOPS.

    What would be better if you replaced "arc" with "problem" and "loop" with "map".

    Arc is thus a problem and loop is a map of problems.

    If a problem is always the same and if the range of possible solution is low the problem would, normally, burn out quickly. Puzzles are of that sort.

    What's different about sports and board games like Chess and Go is that problems are interrelated and kept fresh by the presence of human opposition and controlled randomization.

  5. You definitely should have a look into David Bordwell's chapter on narrative comprehension in his book Narrative in the Fiction Film, published in 1986. I know you will probably not look into it because it is about movies and narrative, but it has great concepts additional to those that you use here. It speaks of how a film presents audio-visual cues that ask the audience to carry out certain operations. Based on the perception and interpretation of these sense-data the audience would form a number of related schemata and set up hypotheses which would be justified or falsified as this loop repeats. It is very similar to what has been referred to gameplay cycle in someone else's article on gamasutra + your model of skill atoms.

    Bordwell distinguishes between a number of schemata (the term schema or model in your "loop" diagram): prototype schemata, template schemata, procedural schemata and style schemata. He later shows how these are related and "chunked" into sequences by the audience. I think it would definitely help you to refine your model even more, and may give you new ideas about the interaction between loops and arcs.

  6. If a player plays a game, and they don't want to play it again, that means they've been changed by the experience. Perhaps they learned something.

    If a player can play a game over and over, then it just amuses them, it doesn't change them.

    I would rather make games that actually teach.

  7. Wow. A lot of comments that obviously didn't follow the train of thought.

    Loops teach. I like the analogy of honing a knife edge. Do it long enough and you'll usually get a really nice sharp edge, but that doesn't mean you can't screw it up and nick the edge. There's an extra wisdom that comes from experiencing a range of failure and success states that a loop may contain. Once you fully explore that space, you'll grasp it a lot better than the "arc" that just tells you how to win. Knowing how, and actually having done it, are two different things.
    I don't believe a loop can be fully consumed. I would like to point at Douglas Hofstadter's strange loops discussion. You can even be self-aware of the loop, but that doesn't excuse you from it.

    Oh, and here's a final thought that may just be trolling. An arc may just be one of many that together form loops that are too meta for us to see or rationally model.

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  9. pinball comes to mind reading this. there is no end. you can beat high scores.. but then again, you can beat that high score.

    anyhow, can you link to sites that define the phrases and words you use? like a wiki? I can't find what an 'evergreen game' is.

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  11. That's a reasonably interesting way to think, actually: I'm not sure how much it applies to a lot of things which aren't games, but for that specific type of programming it's a cool concept. As a programmer, I find that I rarely think about the "story" that the application I'm writing "tells" -- it's more about whether the bits of it work so that the user can make it do what it wants. I guess the difference is that a game has its own ideas about what's going on, which get enacted regardless of what the user does.

    One small (and possibly obstreperous) thing: don't write "to better understand" -- in fact, don't write "to better [verb]" -- it's not English and it kind of ruins the piece by making it seem ill-conceived. use "the better to understand [x]" or, "to understand [x] better". Sorry - had to do it.

    1. ???? What are you talking about. "To better X" is perfectly cromulent. Don't spend your life looking for new normal phrases to get a grammar hate on!

  12. Hi. I didn't use these loops and arcs in my designs, but after reading this article, I 'll definitely try to use these loops and arcs in my next design. Could you please tell me if i got any problem while creating design using these loops and arcs then how can i contact you?

  13. While reading this my wife is playing Triple Town on Facebook, one of my current favourite games on Android. Something that has been missing for me on my phone has been a feeling of progress, something that I see has been added to the FB version. Reading this article makes is very clear what the difference is, the use of arcs to complement a loop gameplay.

    Basically it's the kind of games I install for my mother in law that tends to get it right. Games like Zumba that are in the core very much a loop type of game but still gives a feeling of progression.

    I tried to apply this to another game I've played a lot, World of Warcraft, and realised how complex their model is. They have basically built a game on a very large set of loops strung together loosely by smaller and larger arcs. That model makes the players both feel like they are mastering the loops at the same time as they feel they are traveling forward. The smaller arcs give constant payloads, the loops makes it easy to sit down, the larger arcs give a long term goal.

    I've tried the starwars MMO as well but didn't like it, to much of an arc based game. This article made it very clear why WoW worked for me while StarWars didn't, with my ADHD I need the loops to be able to sit down and feel relaxed. Starting a loop takes a lot less mental energy then starting, or jumping back into, an arc.

    Thanks for a very nice article.