The top rectangle looks like it's moving faster than the bottom rectangle but it isn't GIF

wow. i can't believe you would say that. all rectangles are sexy

I didn't say the bottom one isn't sexy. It's just....less sexy

It doesn't usually work without the stripes, the original version has black stripes which causes a contrast between the rectangles and that's what causes the illusion so I'm not surprised you can't see it.