Though graphical, this demo doesn't use binary image files such as GIF, JPEG, and PNG, but consists only of text data.
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You see 2 disks ● ● .
First of all, close (or cover with your hand) your left eye, and look at the left blue disk ● by your right eye.
Far apart from the display at first, get close to the display slowly and slowly keeping the blue disk ● at the center of the view of your right eye.
If another yellow disk ● disappears on the way to the display, you also have a blind spot, and it's so big that the whole disk ● vanishes!
Disapearing completely, now, what do you see at the place that the disk ● took? White? Black?
If the place is filled by the same background color as that around the disk ●, your "seeing" is nice.
Next, close your right eye and look at the right yellow disk ● by your left eye, and get close gradually. You will have an experience of the same kind.