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Angry Birds and Accessibility Standards

I'm going to use the Web Content Accessibility Guidelines to break down Angry Birds. I'm also going to show how following these standards leads to better usability for everyone.

(This article was originally posted at Ananse Production's website. Click here to read the original article)

Update: Per Sandra's comment game developers interested in accessibility should check out the IGDAs Game Accessibility Interest Group. They seem to be working on a gaming specific set of guidelines.


While trying to look for a set of accessibility standards for the game I'm working on I couldn't find any. While sites like can give really useful papers and statistics about disabled gamers, I couldn't find a clear list of guidelines to follow for making sure as many people as possible are able to play my game. While I understand blind adherence to rules isn't the best way to achieve accessibility, game developers lives are a lot easier when we have a standard list of items to test against.

The closest thing I could find are the Web Content Accessibility Guidelines. They are a set of best practices that should be followed for making a website and its content accessible. Each guideline also comes with an explanation of the reasoning behind it. So for this post, I'm going to use these standards to break down the immensely popular mobile game Angry Birds made by Finnish developer Rovio. In the spirit of the Gamasutra article "Resetting Accessibility in Games" , I'm also going to show how following these standards leads to better usability for everyone.


Angry Birds Main Menu

I'm not including Angry Bird's social network menus in this review. I'm only focusing on content you see after hitting "Play". I'm assuming this is the vast majority of a player's experience in the game. Also, I've only made it up to level 1-21 on my iPhone. I really like the game, I just have next to no free time.

General Gameplay

Relevant Guidelines:

Guideline 1.2: Provide alternatives for time-based media.
Guideline 1.4:
Make it easier for users to see and hear content including separating foreground from background.
Guideline 2.1:
Make all functionality available from a keyboard.
Guideline 2.2:
Provide users enough time to read and use content.


Bird in a slingshot


The core mechanic of Angry Birds is using a slingshot to fling birds at green pigs. The pigs can be protected by ice, wood, metal, or other materials. Some birds have special abilities. Like the blue bird that can split into three and the yellow bird that that can boost its speed in mid air.

A blue bird split into three attacking green pigs


That's it. The core of the game is that simple. No time limits or crazy combination of gestures needed. You don't have to have the "twitch" reaction associated with most modern games. Since "twitch" is something you can only get from other video games, its lack in Angry Birds makes it usable not just for the disabled but by people who aren't used to gaming at all.

Rovio does a good job off using multiple graphical cues to differentiate birds, pigs and obstacles from each other. By making sure the outlines and sizes of the birds and pigs differ significantly, they avoid confusing the color blind [1]. Even for the non-disabled, the variation helps enforce the difference between these objects.

Angry Birds Characters


While not playable by keyboard, the game can be played with only one finger. There's no need for "chording", having to press multiple keys/use multiple fingers at the same time. This helps people with mobility related disabilities like cerebral palsy or arthritis play the game. It also simplifies the game and makes it easier for everyone to pick up and play right away.

Lack of VoiceOver Support

Relevant Guidelines:

Guideline 1.1: Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
Guideline 2.4:
Provide ways to help users navigate, find content, and determine where they are.
Guideline 3.1:
Make text content readable and understandable.
Guideline 4.1:
Maximize compatibility with current and future user agents, including assistive technologies.

Apple's User Interface tech gives apps the ability to tag buttons, labels and other UI elements with accessibility information. When VoiceOver, the iPhone's screen reader, is turned on it can then read that information out loud to blind users. This tech has opened up the world of modern mobile devices to the blind. [2]

However, using Apple's off the shelf tech ties you to iPhone. Rovio, and many other mobile device developers, use their own cross-platform User Interface tech. It makes it easier to not only have a game on the iPhone but also on Andriod and other emerging mobile platforms. Rovio, however, doesn't seem to use any of Apple's accessibility tech since nothing in its User interface is tagged to work with VoiceOver [3]. While there is no true cross platform way for providing accessibility information, WCAG suggest always making the following available from code:  

Name: The name of the element.
What it does.
The state its currently in


This information happens to line up nicely with what Apple's accessibility code expects. Using the sound toggle in the pause menu as an example:

Icon used when sound is turned off in Angry Birds  

Name: "Toggle Sound" 
"Switch Between the sound being off and on" 
"Sound is currently off"

Its worth noting that in a game as visually based as Angry Birds, VoiceOver support is the least of its problems. Even if every label and button was tagged and setup properly, the act of pitching a slingshot to hurl birds at pigs behind obstacles is still fundamentally inaccessible to someone with a visual impairment. I'm learning that its better to make a game fundamentally accessible and not to rely on VoiceOver support to save the day. VoiceOver should be the icing on a cake of general accessibility.

Yay Cake!

User Interface

Relevant Guidelines:

Guideline 1.1:Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
Guideline 2.2:
Provide users enough time to read and use content.
Guideline 2.4:
Provide ways to help users navigate, find content, and determine where they are.
Guideline 3.2:
Make Web pages appear and operate in predictable ways.
Guideline 3.3:
Help users avoid and correct mistakes.

Being a Finnish developer developing for an American market, Rovio must have been very conscious about the need for translating any text in the game. The game's menu doesn't rely on text at all but on intuitive symbols.


Icons used on Pause Menu


The text that's used for level names and numbers isn't important for understanding the game. Even for crucial information, like the secondary abilities of birds, Rovio relies of descriptive pictures and good level design to teach the player.

Bluebird Instructions


The use of symbols instead of text not only makes the job of localization easier but helps players that have trouble reading but can still see well enough to play the game.

Rovio also makes sure to keep the User Interface very shallow. Every important feature is only two taps away. The pause menu only has 5 buttons on it leaving it very uncluttered. Since the levels are small and restarting them is so easy, Rovio doesn't have to implement "undo" functionality to let players fix mistakes. This keeps the game simple which again makes it more usable for everyone.

Other Guidelines

Guideline 1.3: Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
Guideline 2.3:
Do not design content in a way that is known to cause seizures.

I don't think Guideline 1.3 is relevant. If VoiceOver support was implemented Angry Birds could support the standard VoiceOVer gestures. But given some quirks with how input is processed when VoiceOver or Zoom is on, using a slingshot wouldn't be convenient. Messing with that core mechanic would make this another game entirely.

Angry Birds doesn't have any flashing animations which eliminates the risk of seizures. While video induced seizures are relatively rare[4] most people who suffer from them don't know they're susceptible until the first attack. [5]


The WCAG seems like a really good starting point for judging accessibility in games. Not only does it contain the main guidelines above but multiple levels of success criteria to judge how well you've implemented a guideline. See Web Content Accessibility Guidelines for the nitty gritty details.

One thing that's lacking on most platforms is screen reader support. Apple has been ahead of the curve in terms of accessibility and hopefully other platform owners will follow. With the advent of motion gaming being used as a way to entice non-traditional gamers, I'd be disappointed if accessibility isn't on the minds of Sony, Microsoft and Nintendo.

Its also important to note that ease of usability in Angry Birds goes hand in hand with most of these guidelines. Not only can the guidelines be used as a way to accommodate special needs players, but as a way to judge the usability of your game for everyone.

Everyone likes cake!


All images of Angry Birds were captured from my iPhone and used under fair use. Cake images taken from Wikimedia Commons. and

Note 1: According to Wikipedia up 10% of American males are red-green color blind. Color blindness is rare amongst women.

Note 2: Austin Seraphin's account of getting his iPhone

Note 3: For iPhone developer's Apple's guide to Accessibility Programming on iOS. The link shows up in Google searches so I'm assuming this doesn't break iOS NDAs.

Note 4: From the Epilepsy Foundation:

"...the annual incidence of visually provoked seizures in the United States general population is estimated to be one in 91,000. Among young people 7 to 19 years of age – a population that is most susceptible to these provoked seizures and among the most frequent users of video technology – the annual incidence may be five-times as high, or one in 17,500. Only individuals who are susceptible, meaning who are photosensitive, are at risk for developing seizures provoked by light."

Note 5: Also according to the Epilepsy Foundation

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