system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why you see colors when you close your eyes really hard.

I've always wondered why this happens, almost as if the colors dance in and out of sight when I shut my eyes and focus on the backs of my eye lids. Any knowledge on this?
gpt
Sight is caused by the cells at the back of your eye reacting to light. These signals are carried along a wire called the retinal ganglion to the part of your brain that sees.

The cells in your eye and retinal ganglion cells are designed to be stimulated by light, but can be stimulated by lots of things. Pressure on the eyes, electric shock, or very strong magnets.

You can also stimulate the visual area of the brain directly. The visual area is right at the back. A strong impact here will cause you to see "stars", random patterns of light.