Arrows, fish, vortexes and hearts that all look like they're moving. Nothing is. Only the colours change.
What: Nothing here moves. Not one pixel. Every shape just sits there changing colour, and yet the arrows slide, the fish swim off and the vortex sucks you in. It’s a follow-up to my Reverse Phi Rainbows, same trick, just a whole lot more of it. The whole thing is inspired by jagarikin [1], a Japanese artist who posts these on X, and his running joke is sticking an arrow on everything. In his words, the circles aren’t moving at all, “but human brains can’t resist arrows” [2].
How To: Click (or tap) for a new version, there’s a bunch. Don’t stare at one shape, let your eyes wander around, for me it’s strongest just off to the side of where I’m looking. Slower speeds usually work better too. Try Arrow Circles, then switch off Show Arrows. Still moving, right? Now switch them back on and hit Reverse, so the arrows point one way and the motion goes the other. For me the motion wins every time. Grayscale still works, and dragging Edge Width down to almost nothing kills it completely, which is a big clue to how it works.
Explain It: Every shape has two super thin edges, a pixel or two wide, running a little ahead and a little behind its main colour. So along one direction you always see the colour that’s coming next, then the current one, then the one that just left. That’s exactly what a real moving edge looks like to the motion detectors in your eyes, so they fire, even though nothing is going anywhere [3]. It’s called reverse phi (or four-stroke motion if you want to get fancy), and Stuart Anstis has been poking at it since 1970. The arrows barely do anything, the motion lives entirely in those edges, the arrows just tell your brain which way to expect it. And it’s not really about the colours either, it’s the light and dark. Try Two Color, it works just as well.
I've researched these optical illusions in my spare time but am clearly not any kind of expert and my explainations are pretty smooth brained, if you find something mis-cited, earlier examples, or general mistakes please new let me know via toymaker@toms.toys, be kind!