My dad sees the glass as "Hey, I got a glass of water!"
Not one of them is a smart@$s interesting
Technically, all glasses are full, they all contain air in them as well
Try moving the pic up and down at a steady pace
If you zoom in to two row filling the screen and then moving your finger up and down, it looks like the cup change size!!
If you swipe your screen up and down it looks like the glasses are moving