Before you enter
Each chamber fatigues the cones in your eyes on purpose. Afterimages can last several minutes. They are harmless and will fade.
Do not continue if you have photosensitive epilepsy, a history of light-triggered migraine, or if you are currently experiencing eye strain or a headache.
Best conditions: a dark room, the screen as bright as you can stand, an arm’s length away. Rest your gaze on the mark. Do not look away.