system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: That temporary "watermark" on our vision when we look at something bright then either look away or close our eyes?
gpt
The color-sensing cone cells in your eyes need time to "recharge".  When light hits those cells, special molecules absorb the light and are forced to change shape, which activates the nerves in your retina.  When you stare at a bright light, your cone cells are all firing, all of those molecules are getting bent, and when you close your eyes they're stuck bent for just a short while and continue activating your nerves.

The longer you stare at bright light, the more cones are activated and don't have time to fix themselves.