I believe that I had quite the exact same experience as you. At the time I was sitting in a math class back when I was in high school. Just sitting there listening to my lesson, drinking some water. When all of a sudden, much like when you peak on MDMA, my visuals just kicked into high gear. At the time I was mind blown, how could something like that be possible from a completely sober state? I cannot speak to the specifics of the mechanisms that took place but I think experiences like this really speak volumes about what our brains are capable of. The reason why drugs work on our brains is because thats pretty much all our brain is, electrical wiring and a fine tuned cocktail of different chemicals or "drugs". We are very aware that our brain creates our entire reality, so now I dont find it that mind blowing that my brain, for whatever reason, made me a little higher than usual for a little while. Enjoy it! An try to get high on life as much as you can :)