its only bad because combined with OCD, when i try to sleep at night, and i close my eyes i get disturbing closed-eye hallucinations that cause high levels of anxiety. I often mess around with it when i am content though. Like sam said, i sometimes sit in bed and look at my celling fan shadow, if i concentrate hard enough one of the blades will disappear. There are other manipulations i can create if i think hard enough. It just sucks having to OCD and HPPD.

Still i wish i would have known before hand. In some cases it worsens with age.