Dreaming awake. Idk how to call it otherwise.

I invent to myself the most ridiculous stories of things of my imagination and i play them in my head, like a sort of head game.

When i do a sufficiently long story, i often fall asleep on it and i continue it the next evening, and it can last months. Plus you get better at mental visualisation the more you do it. I remember dreams almost every night since i did that for a long time.