Health warning

A small number of people have seizures or blackouts when they see certain flashing lights or patterns, including in video games. It can happen to someone who has never had a seizure before.

If you, or anyone in your family, has had seizures or epilepsy, talk to a doctor before you play.

Stop at once and see a doctor if you notice any of these while playing:

• dizziness or light-headedness
• blurred or changed vision
• twitching of the eyes or face
• jerking or shaking of your arms or legs
• confusion, or losing track of where you are
• a moment you cannot remember
• any movement you did not mean to make

Parents: watch for these signs in children, and ask them how they feel. Children and teenagers are more likely than adults to have these seizures.

• Play in a well-lit room.
• Sit back from the screen.
• Do not play when you are tired or short of sleep.
• Take a break of ten to fifteen minutes every hour.

Timed presses, over and over, are hard on hands and wrists, and a bright screen is hard on eyes. If your hands, wrists, arms or eyes ache or feel tired, stop and rest. If it keeps coming back, see a doctor.

This site flashes too. The footage on it is the game's own, and the page adds sparks, a shake and a shockwave to each parry. If your device is set to reduce motion, the page leaves those out, but the footage itself still flashes.