Experiment · temporal fusion
Between frames
Alternate two frames faster than your eye can follow and the two fuse into a third image that exists on no single frame. A screenshot captures one polarity. A recording aliases them. Your eye sees the blend. One artwork, three audiences.
The stage
Watch it live
Measuring your display's refresh rate…
Your eye fuses the two frames into flat gray. The message is not there.
A screenshot catches exactly one frame, so the message develops.
A recording samples the alternation at its own cadence and makes a third thing — a flip, a crawl, or a freeze, depending on phase.
What a screen recording catches
Illustrative, not measured: how a recorder at N fps samples a 120Hz alternation as the capture phase drifts.
How it works
The frame is not the image
A display shows one compositor frame at a time, but your eye is slow. Above roughly 60Hz of alternation the two frames stop registering as events and fuse into their average. Each frame here is the exact negative of the other, so the fusion is uniform gray — every pixel lands on the same middle value regardless of the display's color math.
A screenshot has no persistence. It records whichever frame was compositing at the instant of capture, so the image that your eye could not see becomes legible — black text on white, or white on black, depending on timing. The same file, perceived three ways.
This is the inverse of the usual ambition. Most images are built to survive being screenshotted; this one is built to be betrayed by it.
The safety gate
Why it refuses to run below 120Hz
Alternating two frames on a 60Hz panel means each appears at 30Hz — inside the 3–30Hz band
that can trigger photosensitive seizures. Fusion only starts when the panel is measured (from
requestAnimationFrame timing, not its sticker rate) at 120Hz or faster, which
keeps the effective flicker at exactly 60Hz. It also honors
prefers-reduced-motion, and a paused state stays available to anyone.
The gate isn't a one-time check. Browsers can throttle requestAnimationFrame to
60Hz after the page loads — battery saver, thermal limits, or a panel that switches refresh
rate. If the alternation ever runs slower than the safe cadence, the page halts itself on a
single frame rather than risk dropping into the flicker band. Most phones since 2021 and
recent Mac laptops refresh at 120Hz, but browsers throttle under the conditions above, so
this page measures rather than assumes. If you're seeing a frozen frame, that's the gate
working.