Xbox Accessibility Guideline 118: Photosensitivity
Goal
The goal of this Xbox Accessibility Guideline (XAG) is to help prevent players from experiencing negative or potentially harmful side effects during gameplay, including photosensitive seizures and migraine episodes.
Overview
A small percentage of people (approximately 1 in 4,000) can experience a seizure when they're exposed to certain visual images, including flashing lights or patterns that might appear in video games. Even players who have no history of seizures or epilepsy might have an undiagnosed condition that can cause photosensitive epileptic seizures while watching video games. Many players might be unaware that they have epilepsy until they experience their first seizure. This is why eliminating game content that can potentially cause photosensitive seizures is preferred over splash-screen warnings or other methods.
These seizures can have a variety of symptoms, including lightheadedness, altered vision, eye or face twitching, jerking or shaking of the arms or legs, disorientation, confusion, or momentary loss of awareness. Seizures can also cause loss of consciousness or convulsions that can lead to injury from falling or striking nearby objects, as well as death.
In addition, repetitive flashing images can be problematic for a wide range of other players; for example those who are autistic, prone to migraines, or have sensory processing disorder.
Scoping questions
Does your game have any visual elements?
- All games should be tested for photosensitive seizure triggers, regardless of whether the game includes intentional flashing.
Implementation guidelines
- Games shouldn't include images/experiences that might cause adverse reactions, such as seizures or migraine episodes, during gameplay.
To help reduce the chance of adverse reactions, avoid the elements that are defined as follows.
Luminance flash failure
Definition:
A flash is defined as a 10% change in luminance (where 100% is the maximum luminance of a white screen)
The darker luminance value should be below 0.8.
Failure criteria:
Flashes occur too frequently (approximately more than three per second).
Flashes take up a certain amount of the screen (approximately 20 percent or more).
Lower intensity flashing can also cause a failure if it's continued for an extended period of time.
How to address:
Reduce the contrast between the brightest and darkest parts of the flash.
Reduce the frequency of the flashing.
Decrease the size of the flashing.
Red flash failure
Definition:
A red flash requires a lower change in luminance than a normal flash. Specifically, it applies when either extreme of the flash is a saturated red (R/(R + G + B) >= 0.8).
A flash here is defined when the change in the value of (R-G-B) × 320 is greater than 20.
Failure criteria:
Flashes occur too frequently (approximately more than three per second).
Flashes take up a certain amount of the screen (approximately 20 percent or more).
Lower intensity flashing can also cause a failure if it's continued for an extended period of time.
How to address:
Desaturate the red coloring.
Reduce the contrast between the brightest and darkest parts of the flash.
Reduce the frequency of the flashing.
Decrease the size of the flashing.
Spatial pattern failure
Definition:
- Alternating bands that have high contrast define a spatial pattern.
Failure criteria:
The difference in contrast is greater than 10 percent.
The pattern takes up a large part of the screen (approximately 20 percent or more).
How to address:
Reduce the contrast between the bands.
Decrease the size of the pattern.
Potential player impact
The guidelines in this XAG can help reduce barriers for the following players.
| Player | |
|---|---|
| Players with cognitive or learning disabilities | X |
| Other: players who experience photosensitive epileptic seizures or have sensory processing disorder | X |
Resources and tools
| Resource type | Link to source |
|---|---|
| Website | Epilepsy Society (external) |
| Website | Photosensitivity and Seizures - Epilepsy Foundation (external) |
| Tool | Harding FPA Test - Cambridge Research Systems Ltd (external) |