I've been developing a game which is rather blinky in terms of color and brightness contrasts. It's an iPhone game, so the screen will be quite small, but I've heard about Wipeout XL failing the epilepsy test.
How does one ensure that a game won't cause epileptic seizures for users?
I am an indie developer, so a low-budget solution would be ideal.
There is software available to perform epilepsy testing as defined by OFCOM, known as the Harding Test.
Unfortunately, the software seems to be commercial only and requires a data capture card for it to run, so it's not the most financially feasible solution for an indie dev. This can be found here: http://www.hardingfpa.tv/
However, there is an alternative for smaller companies at http://www.hardingtest.com which has reasonable rates without needing a dedicated machine to carry out the testing for you (you just upload a video of gameplay) - £75 for under 30 minutes, which isn't too bad.
A warning should be more than sufficient and covers your back should anything unfortunate arise from a user playing your game, but if you do want to get it tested, the option is there.
A group that studied the Pokemon epilepsy phenomenon came up with the following recommendations:
Flashing images should not be displayed for a total duration of more than two seconds.
Stripes, whirls and concentric circles should not take up a large part of the television screen.
Note that these are just recommendations, not cut-and-dry human thresholds for epileptic triggers. If your game violates any of these guiding principles, there is a good chance it may be dangerous; however, if it doesn't, that's still no guarantee that it is safe.
Sources: http://en.wikipedia.org/wiki/Denn%C5%8D_Senshi_Porygon http://onlinelibrary.wiley.com/doi/10.1111/j.0013-9580.2004.18903.x/abstract
You cannot make sure that your game will not trigger seizures, ever, since the thresholds differ by orders of magnitudes between individuals and beetween the same person on different days and under influence of a hundred other factors which you cannot know about (lighting conditions, distance to the display, sleep deprivation, stress level, background noise, alcohol intake, etc).
If you can, that is if it doesn't disturb the game's look and feel, you may try as jokoon said, reduce the flashing a bit. If that would "destroy" the game's look and feel, scratch the idea.
Regardless, if you see a reasonable possibility that your game might trigger epileptic fits, you should add a (loosely worded) warning somewhere on the download page or on the package.
Something like "Note: This game contains vivid graphics. Video games (in general) may cause...". This will give people who have a known seizure disorder a valuable hint, and that is as much as you can do -- for them, and for yourself.
You cannot prevent people from having seizures, but you can prevent them from filing a lawsuit against you claiming that you didn't warn them.
I would however avoid saying "This video game may cause..." because that would be
a) massively negative marketing and
b) possibly the opposite effect of what a disclaimer should achieve (one could argue: "Hey wait, you knew this game was designed in a dangerous way and you still sold it?")
I wouldn't trust internet on that. I'd prefer asking a doctor, an ophthalmologist or a neurologist. The only thing I think I'm sure I know (and shouldn't be trusted), is that epileptic reactions are caused by blinking colors, meaning: very different colors (mainly meaning the hue component of the color) alternating at some kind of some particular threshold frequency; this may be linked to the fact the human eye cannot perceive animation beyond 60Hz.
This is tightly linked to how the brain computes back and perceive images, but maybe and especially motion.
To be sure you won't trigger crisis in anybody, document yourself or ask somebody who has a speciality: epilepsy is not well known because it's part or neurology.
Try to make your game somewhat less blinky, blinking less rapidly or just fade; it will be more quiet for the eye/brain. Remember our brains aren't supposed to be used to artificial images and motion, so the more the thing you render compares to reality the more the better.
Here is some guidance: http://gameaccessibilityguidelines.com/avoid-flickering-images-and-repetitive-patterns
Bottom line is that you cannot test for epilepsy. Any game can cause a seizure. All you can do is test for common triggers.
If in doubt and if the effects can't be avoided, give people advance warning, and ideally an option to disable the effect. But don't say things like 'epilepsy safe mode', you're opening yourself up to a world of legal pain then. Just talk about the effect, e.g.
"this game contains flickering effects. They can be turned off in the settings menu"
