That was seriously uncool and no fun. I almost immediately saw crosshatching bars and shapes maybe like fractals, and then the center of the screen seemed to form a white sphere and a f'ing nightmare came crawling out of it filling me with dread, and then I closed the page. Took about a minute.
Did it a second time maybe 30 minutes later and it quickly resolved into spinning wind turbines blades, dozens of them, circling the middle of the screen, in a random circle-ish flow that moved like waves. After a few minute of that, it seemed like I was falling through a warp tunnel with stars connected by glowing arms flashing by, then hands and arms started to reach up from the bottom of the screen and I turned it off.
I just let my eyes relax and didn't really focus on the screen, but when I did focus, that's usually when the unpleasant images appeared.
I had bouts with nightmares and such and a technique I found is that when the horrors begin to appear, I consciously try to be unaffected by them. To try to at least delay what you just described, that feeling of dread taking over you. While you can't really have control over the outside world and the horrors within it, you can at least have control over your reactions to it. And reactions to stimuli like this red flashing thing, and many other situations, are really about just the reaction of the mind, filling in the blanks, trying to make sense. The more you can relax that effort, the less horrific it will become. Similar to relaxing a muscle cramp. I'm not saying that I'm very good at this all, but going this way has helped me a lot already.
I saw spinning shapes too: spirals, figure eights, spheres of rainbow pointillist light. Or just swirling patterns like schools of fish. They all moved slowly. When I tried to focus they just disappeared. For me it was relaxing. I watched for about 5 minutes.
Sounds like what I see when I press my fingers (gently) onto my closed eyelids. I think it's the different layers of the visual cortex trying to find edges/patterns in something that doesn't have any.
Did it a second time maybe 30 minutes later and it quickly resolved into spinning wind turbines blades, dozens of them, circling the middle of the screen, in a random circle-ish flow that moved like waves. After a few minute of that, it seemed like I was falling through a warp tunnel with stars connected by glowing arms flashing by, then hands and arms started to reach up from the bottom of the screen and I turned it off.
I just let my eyes relax and didn't really focus on the screen, but when I did focus, that's usually when the unpleasant images appeared.