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Accessibility for The Last of Us Part II

Video Games

Naughty Dog developers and accessibility consultants

Earlier this year we wrapped up four years of development and shipped The Last of Us Part II. While most of my work was on systems, combat, and AI, I also co-headed our effort to push the boundaries of accessibility.

We established our goals early in preproduction. We wanted to build on the motor accessibility features from Uncharted 4, offering more options for players to customize controls and simplify inputs. We wanted to have scale, colour, and contrast options for our HUD and subtitles. Most ambitiously, we wanted to create a suite of features that would allow a blind player to complete the game without sighted assistance. By the time the game shipped, we had developed over 60 accessibility features.

To hear a full breakdown of our development process, check the talk that Emilia Schatz and I recently presented at GAConf. We discuss how we planned our production, worked with terrific consultants, iterated on our features, and integrated accessibility into our regular playtesting. Many thanks to Ian Hamilton and Tara Voelker for inviting us to speak.

GAConf logo

Accessibility in The Last of Us Part II:
A 3-Year Development Journey

After years of development, it’s been so exciting to see the reactions from fans about how these features have benefited them. Some have called The Last of Us Part II “the most accessible game ever”. The story also got picked up outside of the video game press, with coverage from CNN, BBC, CBC, and USA Today; Emilia and I even had a radio interview with NPR Morning Edition.

Our dearest hope is that our push for accessibility helps advance the state of the art in the games industry and inspires other developers to make it a priority. Many thanks to our accessibility consultants and testers, our collaborators at SIE Worldwide Studios, and everyone at Naughty Dog who helped make these features possible.

Photo credit: Misty Rayburn

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Combat Design & AI in Uncharted 4

Video Games

Matthew Gallant speaking at GDC 2017

Back in 2017, I gave my first talk at GDC about combat design and AI in Uncharted 4. A recording of this talk is now free and publicly available in the GDC Vault.

Authored vs. Systemic:
Finding a Balance for Combat AI in Uncharted 4

The title of the talk comes from the biggest quandary we faced through development: how to decide what to handle systemically (using generic combat AI systems) and what to author (hand-placed markup and scripting). Previous games in the Uncharted series were highly authored, but we had some new design goals for Uncharted 4. As we pursued much larger wide-linear spaces and deeper stealth gameplay, we knew our familiar scripted approach would struggle to account for all the ways the player could engage in combat.

This led us to explore a more systemic approach to combat design. For instance, we developed the concept of “vantage” in an attempt to programmatically analyze combat spaces and find the strong positions to hold. We tried a similar technique for getting enemies to search, generating “heat” at the player’s last known location that would realistically disseminate through the layout. Unfortunately, both of these approaches failed to generate consistent results. We had oversteered away from authored combat design, and needed to find a balance.

We eventually developed the concept of “hard points”, which allow level designers to mark up strong positions and important places to defend. However, the choice of whether to use these hard points and which NPCs to assign to them is left entirely up to the systemic combat logic. This hybrid approach let us leverage the designer’s holistic knowledge of a space without requiring bespoke scripting to account for every possible scenario. We felt like this was the middle ground between “authored” and “systemic” approaches, and that it gave us the best of both extremes.

The full talk goes into much greater detail on the development process and implementation details, so check it out if you’re interested. As a bonus, you’ll also discover what Uncharted has in common with Pac-Man.

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Blocktober 2018

Video Games

Last year, my friend and coworker Michael Barclay boldly declared that “level blockouts are art”. He started the hashtag #Blocktober to celebrate the art form and encourage other developers to share screenshots of their blockmesh levels. The response was enthusiastic, as hundreds of developers gave us a sample of their early-production work. It provided some well-deserved exposure to a vital facet of game development that players normally never get to see.

Since Michael is starting up #Blocktober again this year, I thought I would dig through my own work files to find something to share. While I’m not actually a level designer, in my systems design work I often develop playable prototypes to pitch a certain gameplay idea or feature.

The video above is an early prototype of the train combat sequence that was later developed for chapter 9 of Uncharted: The Lost Legacy. While we were still in early preproduction, I wanted to pitch an action setpiece that combined ideas and mechanics from two of my favourite levels: the train from Uncharted 2 and the convoy chase from Uncharted 4. This would also enable us to leverage some of the physics and animation tech that had already been developed in our engine.

A few credits: the rocky terrain that the train meanders through is borrowed from Mark Davies’s blockmesh of the islands from chapter 12 of Uncharted 4. I reused many of the vehicle-to-vehicle combat systems previously developed by Kurt Margenau. I also wasn’t involved with the real train level that actually shipped with The Lost Legacy; that was developed from scratch by Nicholas Lance, Asher Einhorn, Michael Barclay, Vinit Agarwal and many more.

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Thinking in Systems

Books, Video Games

Book cover of Thinking in Systems: A Primer by Donella Meadows

There is a certain class of books (Understanding Comics, The Design of Everyday Things) that aren’t ostensibly about video games, but have still found their way into the informal game design canon. Having recently read Thinking in Systems: A Primer by Donella Meadows, I believe it also deserves a spot on that list. The book covers a wide range of tools and methods for systems thinking, but I’d like to focus on one technique in particular and how it could apply to game design.

Stock-and-flow diagrams are used to model the interconnections between elements of a system. As the name suggests, they define systems in terms of stocks and flows. Stocks are “the elements of a system that you can see, feel, count, or measure at any given time”; they are shown as boxes.

Flows are what cause stocks to change over time. Inflows and outflows are depicted as thick grey arrows (going to or coming from a stock, respectively). The rate of a flow is represented by a faucet, because it can be adjusted higher or lower.

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If the rate of a flow changes based on the level of a stock, then this creates a feedback loop. There are two types of feedback loops. Balancing loops seek to maintain equilibrium and resist change within a system (in game design this is often called negative feedback). Reinforcing loops are the opposite; they enhance any direction of change imposed on the system (positive feedback). In stock-and-flow diagrams, feedback loops are represented by thin curved lines.

Clouds represent the boundary of the system. The boundary is an intentional choice of what is considered inside and outside the system for the purpose of analysis and conversation. In reality, “there are no separate systems. The world is a continuum.” The boundary only exists in our mental model, and thus it must occasionally be reevaluated to suit the problem at hand.

Here’s a simple real-world example as given in the book.

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In this example, the temperature in a room is a stock. Heat flows into the room from the furnace, and the rate of inflow is determined by the thermostat. It turns the flow on/off based on the difference between the temperature in the room and the goal temperature setting. Heat also flows out to the air outside. The rate of outflow is determined by the discrepancy between the indoor and outdoor temperatures. The rates of inflow and outflow are both affected by the current level of the temperature stock, which indicates that we have two feedback loops (both balancing).

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Intentionality & Improvisation

Video Games

[Left] Lightning strikes in Breath of the Wild / [Right] Grass burns in Far Cry 2

While I was playing The Legend of Zelda: Breath of the Wild over the holidays, I kept thinking about Far Cry 2. Of course that’s not uncommon; I cut my teeth writing about games in ~2008, so I tend to see Far Cry 2 everywhere (game design pareidolia). However, rather than a vague impression, Breath of the Wild evoked specific ideas that director Clint Hocking explored in a 2009 GDC talk entitled “Fault Tolerance: From Intentionality to Improvisation”. I’d like to use that talk as a framework to compare the two games and discuss some common mechanics that are used to similar effect.

Clint begins his talk by discussing intentionality in games, which is “the ability of the player to devise his own meaningful goals through his understanding of the game dynamics and to formulate meaningful plans to achieve them.” Games that support high-level intentional play (e.g. immersive sims, stealth games) tend to have “robustly interconnected systems”. The player must develop a deep understanding of both how these systems work in isolation and how they interact with each other.

The flow of play can be divided into two phases: a composition phase (deciding and figuring out what to do) and an execution phase (doing it). Games that favour execution are more “ride-like” (Call of Duty), whereas favouring composition is more “puzzle-like”. Intentional play emerges when the two phases are kept in a “game-like” balance.

Clint notes that messy systems (generalized physics, crowds, fire) tend to collapse the player’s intentionality. However, he also felt that the “simulation of broader more chaotic and unpredictable systems” was the future of game design. Thus, with Far Cry 2, Clint’s initial goal was to explore how highly intentional play could be preserved in a “highly dynamic and free-form” environment.

At one point later in development, Clint and his team decided that some of the high-level faction systems they’d been developing needed to be cut. However, he was concerned that this would discourage the player from making complex plans. Shortening the composition phase might make the game more “ride-like”, which would subvert intentional play.

However, he observed that systems that inflict “small unpredictable losses” (malaria, wounding, gun jams, grenade rolling down a hill) kick the player out of the execution phase and force them to improvise. The player therefore “switches back and forth between composition and execution several times in a given battle”. A short composition phase is balanced by a short execution phase, and intentionality is preserved.

Improvisational play is therefore “intentionality compressed”, and randomness is “the pressure cooker that pushes the already intentional player to react and improvise a new plan on the fly.”

A graph showing an oscillation between composition and execution.

In this vein, Breath of the Wild has two systems that inflict small semi-unpredictable losses on the player. The first is the weapon degradation system. Weapons are fragile, which makes them unreliable. When their weapon breaks, players are forced to adapt. They can pull an alternate (perhaps less familiar) weapon from their inventory, or try to make use of whatever environmental tools are currently on hand. One streamer observed that weapon degradation naturally pushed him to explore the game’s other mechanics, such as stealth and fire.

The weather system can also work against the player. Snow and sandstorms are blinding. Thunderstorms unleash lightning strikes against metal equipment. Most commonly and annoyingly, rain makes climbing just about impossible. Unlike previous games in the series, the player also has no tools (e.g. Song of Storms) to control the weather. When inconvenient weather rolls in, their only real options are to pass the time or adapt their plans.

These chaotic systems therefore serve the same purpose in Breath of the Wild as they do in Far Cry 2: inflicting random small losses on the player to force them back into the composition phase. Unexpected setbacks compel the player to slow down, to observe, and to think; it may even push them to engage with systems that they may otherwise have ignored. Even in her annoyance with Zelda’s weather system, Patricia Hernandez pointed out that: “without these rain mechanics, I wouldn’t have all these ridiculous stories, huh?”


Video by Alex Wiltshire

Another aspect of improvisational play is how the player handles having their plans upset (i.e. being kicked out of the execution phase). As Clint points out, in a “ride-like” game, this usually means just dying and restarting from the last checkpoint. In a more intentional stealth game, the player may be able to recover from a loss, but the cost of failure is so high that they’re just as likely to just quickload the last save.

To encourage improvisation, the player must be willing to fall back into that composition phase (rather than simply reloading). This means that any random unpredictable losses have to be quite small. As Clint points out: “you rarely die from these events – unjamming a weapon takes no more time or effort than reloading does.” Furthermore, the game generally needs to be forgiving of the player’s mistakes.

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