Yin Yang Spinner

yinyang.odd.place

A yin yang you can drive like a motor or flick like a fidget spinner, alone or with friends in a shared room, and a lesson in how screens fool your eyes.

What’s going on

Spin it slowly and it simply turns. Spin it fast and strange things happen: it freezes, it flickers between its two colors, it creeps backwards. Nothing is wrong with the drawing. Your screen only shows a fixed number of pictures a second, usually 60, and when the spin lines up with that rhythm, each picture catches the symbol in almost the same place.

It's the same stroboscopic effect that makes wagon wheels roll backwards in old westerns and helicopter blades hang still in phone videos.

The numbers, on a 60 Hz screen

3600 RPM is 60 turns a second: exactly one turn per frame, so it looks perfectly still.
3590 RPM falls a sliver short each frame, so it seems to turn slowly backwards.
1800 RPM is half a turn per frame. A yin yang turned half way is itself with the colors swapped, so it flickers between the two.
1790 RPM flickers and drifts.

On a 120 Hz phone or laptop the magic speeds double (7200 is out of range, but 3600 gives the half-turn flicker). Clips are filmed at 30 frames a second, so they show their own version of the effect.

How to use it

Motor mode

Speed: drag the slider from −5000 to 5000 RPM. Negative spins counter-clockwise. The number buttons jump straight to the interesting speeds.
Stop / Start pauses the spin where it is.

Try 3600 and then nudge the slider a few RPM either way. Try it on a phone and a laptop: different screens give different results.

Fidget mode

Flick the symbol with a finger (or drag and let go with a mouse) to set it spinning. The faster the flick, the faster it spins.
Flick again the same way to speed it up, or the other way to slow it down or reverse it.
Touch and hold to brake it; a still finger stops it, just like a real spinner.
Friction sets how quickly it winds down, from 0% (spins forever) to 100% (stops almost at once). Brake stops it dead.
On a keyboard: → or ↑ flicks it one way, ← or ↓ the other, Space brakes.

Flick it past 3000 RPM and watch for the same freezing and backward-running tricks as it slows through the magic speeds.

Sound

Vibrate (on phones that can, most Android phones; iPhones don’t allow it for web pages) gives a pulse each time it goes round; spin it fast and the pulses run together into a buzz. Like sound, it’s yours alone in a room.

Tick Sound and set the volume. You hear a swish on each flick, a click every time it goes round, and a bearing hum that rises with the speed. At high speed the clicks blur into the buzz, as they do on a real spinner. It works in motor mode too. Phones need a tap before sound can start, and silent mode must be off.

Theme

Tap a swatch: Classic, Neon, Ocean, Nature, Sunset, Fire, or the rainbow one, Psychedelic. Psychedelic’s colors drift through the spectrum, the symbol and the background blending as they go, and the faster it spins the faster the colors race and the brighter the background glows.

Background, centering and size

Background picks any background color, separate from the color scheme; Theme goes back to the scheme’s own background. A chosen background stays when you change schemes, even Psychedelic.
Center puts the spinner in the exact middle of the screen; Size scales it from 20% to 100% of the screen.
Every slider has − and + buttons for one-step changes; hold one to keep stepping.

Rooms: spin together

Press Room, type a name (letters, numbers and dashes) and Join. Anyone who joins the same name, on any device, spins the same spinner.
Whatever anyone does is shared: flicks, braking, turning it slowly by hand, motor or fidget mode, the speed, the friction, the colors and background, centering and size. Someone who joins later starts in step with everyone else.
Sound and volume stay your own; nobody else can turn your sound on or off.
Copy invite link copies a link that drops a friend straight into the room. A share made while you’re in a room carries it too.

Full screen and auto-hide

Full screen fills the screen with the spinner (where the browser allows it; iPhones don’t).
Auto-hide fades every control and button away after a couple of seconds, leaving just the spinner. Flicking doesn’t bring them back; touch the top-left corner, where the menu button sits, and they snap back (that touch only wakes them; touch the menu button again to open it). They never fade while the menu or share window is open or while you’re using a control.

Press the share button (top right). It takes a picture of what's on screen and makes a link preview for it. Add a title if you like, then post it to Facebook, copy the link, or send it another way.

Clips: choose a shape (a 9:16 reel or a square) and a length, then Record a clip. The menu buttons hide while it films; press Stop to end early. You can keep playing with the controls while it records. The clip can go on your share page, be saved, or be posted as a Facebook reel.

Each share gets its own page with the picture, the clip if you made one, and a button that reopens this app with your exact settings.

Credits

The taijitu, the yin yang symbol, comes from Chinese philosophy: two opposite forces, each holding a seed of the other.

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Made by Jason Buchheim for odd.place.

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