04無限バー

<main class="stage">
  <div class="bar" role="progressbar" aria-label="処理中">
    <span class="bar__fill" aria-hidden="true"></span>
  </div>
</main>

@use "../../../../site/static/demo-tokens" as *;

$duration: 1.5s;                                  // 막대가 한 번 오가는 시간
$easing: ease-in-out;
$color: $subject-blue;                            // 막대 색

@include stage($stage-paper);

.bar {
  position: relative;
  width: clamp(180px, 60vw, 280px);
  height: 6px;
  border-radius: 999px;
  background: rgba($subject-ink, .12);
  overflow: hidden;
}
.bar__fill {
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: $color;
  transform-origin: left center;                  // width 대신 transform 으로만 움직인다
  animation: sweep $duration $easing infinite;
}

@keyframes sweep {
  0%   { transform: translateX(-100%) scaleX(.3); }
  50%  { transform: translateX(20%) scaleX(.6); }
  100% { transform: translateX(100%) scaleX(.3); }
}

@media (prefers-reduced-motion: reduce) {
  .bar__fill { animation: none; transform: translateX(0) scaleX(.55); opacity: .7; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.bar {
  position: relative;
  width: clamp(180px, 60vw, 280px);
  height: 6px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.12);
  overflow: hidden;
}

.bar__fill {
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: #2f6df6;
  transform-origin: left center;
  animation: sweep 1.5s ease-in-out infinite;
}

@keyframes sweep {
  0% {
    transform: translateX(-100%) scaleX(0.3);
  }
  50% {
    transform: translateX(20%) scaleX(0.6);
  }
  100% {
    transform: translateX(100%) scaleX(0.3);
  }
}
@media (prefers-reduced-motion: reduce) {
  .bar__fill {
    animation: none;
    transform: translateX(0) scaleX(0.55);
    opacity: 0.7;
  }
}

import type { CSSProperties } from "react";
import styles from "./IndeterminateBar.module.scss";

export type IndeterminateBarProps = {
  /** 막대가 한 번 오가는 시간 (기본 1500ms) */
  duration?: number;
  /** 막대 색 */
  color?: string;
  /** 트랙 너비 */
  width?: number;
  label?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--color"?: string; "--width"?: string };

export default function IndeterminateBar({
  duration = 1500,
  color = "#2f6df6",
  width = 220,
  label = "Processing",
}: IndeterminateBarProps) {
  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--color": color,
    "--width": `${width}px`,
  };
  return (
    <div className={styles.bar} style={vars} role="progressbar" aria-label={label}>
      <span className={styles.fill} aria-hidden="true" />
    </div>
  );
}