A Fantastic Optical Illusion: Just Another Brick in the Wall?

I love optical illusions, especially ones that really twist your brain around. I saw one recently that really had me going for a minute. And it's not so much the illusion itself that really gets me, but my own brain's reaction to it. The photo is above. I saw it on a Facebook post from this week, though it's been around since at least 2014.* It shows a brick wall, seen at a shallow angle, with somewhat large gaps between the bricks. The bricks are red, and it appears that there's a small gray ro...