Liquid Fill

// No hooks or handlers, so this stays a server component. The level is a CSS
// custom property, so a consumer drives it with an inline style rather than
// re-rendering anything.
const css = `
.fill {
  --level: 62%;
  position: relative;
  width: 132px;
  aspect-ratio: 1;
  border-radius: 50%;
  overflow: hidden;
  background: #100d1e;
  box-shadow:
    inset 0 0 0 2px rgba(255, 255, 255, 0.14),
    0 14px 34px rgba(0, 0, 0, 0.5);
  isolation: isolate;
}

/* The wave is a SQUARE with a soft border-radius, rotating. Where its rounded
   edge crosses the fill line you see a crest; as it turns, the crest travels.
   That is the whole illusion — no path, no canvas, no per-frame maths. A
   border-radius near 42% is the sweet spot: at 50% it is a circle and the edge
   is flat to the eye, at 0% the corners read as corners. */
.fill__wave {
  position: absolute;
  left: 50%;
  /* Top of the square sits at the fill line; the body below it is the liquid. */
  top: calc(100% - var(--level));
  width: 210%;
  aspect-ratio: 1;
  border-radius: 42%;
  transform-origin: 50% 50%;
  animation: fill-turn 7s linear infinite;
}

.fill__wave--a {
  background: linear-gradient(180deg, #ff3d81, #b45bff 60%, #5b8cff);
  opacity: 0.95;
}

/* A second wave turning the other way at a different rate. Two crests moving
   in opposite directions interfere, so the surface never looks like one object
   spinning — which is exactly what a single wave looks like. */
.fill__wave--b {
  background: linear-gradient(180deg, #4affd0, #22a7ff 70%, #5b8cff);
  opacity: 0.55;
  animation: fill-turn-rev 11s linear infinite;
}

@keyframes fill-turn {
  from { transform: translate(-50%, 0) rotate(0deg); }
  to   { transform: translate(-50%, 0) rotate(360deg); }
}
@keyframes fill-turn-rev {
  from { transform: translate(-50%, 0) rotate(360deg); }
  to   { transform: translate(-50%, 0) rotate(0deg); }
}

/* A specular arc so the sphere reads as glass holding liquid, not a flat disc
   with a pattern in it. */
.fill__gloss {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(40% 30% at 32% 20%, rgba(255, 255, 255, 0.5), transparent 70%),
    radial-gradient(90% 70% at 50% 120%, rgba(0, 0, 0, 0.45), transparent 60%);
  pointer-events: none;
}

.fill__value {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  font: 650 22px/1 system-ui, sans-serif;
  color: #fff;
  text-shadow: 0 1px 10px rgba(0, 0, 0, 0.65);
}

@media (prefers-reduced-motion: reduce) {
  .fill__wave { animation: none; transform: translate(-50%, 0) rotate(8deg); }
  .fill__wave--b { display: none; }
}
`;

export function LiquidFill({ value = 62 }: { value?: number }) {
  return (
    <>
      <style>{css}</style>
      <div
        className="fill"
        role="progressbar"
        aria-valuenow={value}
        aria-valuemin={0}
        aria-valuemax={100}
        aria-label="Uploading"
        style={{ ['--level' as string]: `${value}%` }}
      >
        <div className="fill__wave fill__wave--a" />
        <div className="fill__wave fill__wave--b" />
        <div className="fill__gloss" />
        <div className="fill__value">{value}%</div>
      </div>
    </>
  );
}