Daaar

Even weed can stimulate a flashback, I had one after smoking skunk, nothing happened immediately after, but when I got home the flowers on my wallpaper were within diamonds that were rotating, and the carpet had a lava lamp effect with the highlights. I dunno how much this is relevant to my HPPD, because I never normally "trip" normally, and if I do then it's very mild.

There is cells within the eye that sense movement, watching the spiral thing (or on YT) can tire those neurons out, so when you've looked at it long enough the eye continues to see the movement but not register it. So the "movement" that is happening afterwards is just your brain catching up with what the eyes failed to present to it in good enough time.

I feel like every LSD, research chemical or hallucinogenic I took gave me a piece of a jigsaw, and then on the last trip I had which was really intense and scary. I actually saw it happening every time I tripped though, within my minds eye a jigsaw piece on its' own, then the next time another was added (it looked like the screen on Catchphrase). I don't understand how a theme can reoccur in more than one trip, and how I'm still haunted by it now. The bad trip I had convinced me to stop, I imagined dying, then God told me it was something to do with a years worth of consistent legal high use being drilled out of me all at once. But I can see exactly what you mean, TBH it's actually a bit headwrecking for me that you figured it out.

Mine usually go dark purple/blue or black no matter what colour it was. I have small black afterimages that are just small dots, they never go away and they often turn into holes or spiders when I look at bright surfaces.

The visuals are not a bad part for me, everything seems HD and the synesthesia I see in my head sometimes when listening to music is wonderful, well some visuals can be bad. The worst for me is being delusional at times. Most of the time I believe I actually died on my last trip (it was a research chemical, labeled as LSX) and I am now either living in the afterlife or passing time in a coma, whenever anything happens now I see it as being weird and proof that life isn't real. Sometimes when in crowded places I hear people talking around me, but I always mistake what they're saying, like once I could actually hear two people next to me talking as if they were doctors in a hospital checking up on me, so I believed I was in a coma. It's not too bad anymore I try to avoid crowded places, the auditory hallucinations have faded slightly over the past few months. Now I just see dark dots on stuff, and when I'm awake too long the room flashes and objects wobble in poorly lit conditions.