Ambient, aspect-locked motion embed for seedance/kenburns B-roll — autoplays muted, loops, falls back to a poster still under reduced-motion
No controls, no audio, no interaction — a flythrough is decoration. It autoplays muted and loops. The box is aspect-locked from the first frame, so the poster → decoded-frame swap never shoves layout.
Under prefers-reduced-motion: reduce the clip does not play — it shows a still
poster instead (ambient motion is exactly what the preference asks to suppress). Toggle your
OS "reduce motion" setting to see the flythroughs above collapse to their posters live.