Tetris effect

https://en.m.wikipedia.org/wiki/Tetris_effect

They may see colored images of pieces falling into place on an invisible layout at the edges of their visual fields or when they close their eyes

Interesting, I work as an agronomist and get this if I’ve been scouting for some problem that requires special focus to find, like cutworms, for prolonged periods of time. I’ll get faint images of them when I close my eyes.

Not disturbing in the slightest, I just knew I’d been hard at it.