06Hai dòng chạy ngược chiều

<main class="stage">
  <div class="marquee">
    <div class="marquee__row marquee__row--fwd">
      <div class="marquee__track">
        <span class="marquee__chip">DESIGN</span>
        <span class="marquee__chip">MOTION</span>
        <span class="marquee__chip">LAYOUT</span>
        <span class="marquee__chip" aria-hidden="true">DESIGN</span>
        <span class="marquee__chip" aria-hidden="true">MOTION</span>
        <span class="marquee__chip" aria-hidden="true">LAYOUT</span>
      </div>
    </div>
    <div class="marquee__row marquee__row--rev">
      <div class="marquee__track">
        <span class="marquee__chip">CSS</span>
        <span class="marquee__chip">SCSS</span>
        <span class="marquee__chip">REACT</span>
        <span class="marquee__chip" aria-hidden="true">CSS</span>
        <span class="marquee__chip" aria-hidden="true">SCSS</span>
        <span class="marquee__chip" aria-hidden="true">REACT</span>
      </div>
    </div>
  </div>
</main>

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

$duration: $dur-loop;
$easing: linear;
$color: $stage-ink;

@include stage($stage-yellow);

.marquee { width: min(320px, 84vw); display: grid; gap: 12px; }
.marquee__row { overflow: hidden; }
.marquee__track {
  display: flex;
  width: max-content;
  animation-duration: $duration;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
.marquee__row--fwd .marquee__track { animation-name: marquee-scroll; }
// 같은 애니메이션을 그대로 쓰되 animation-direction 만 뒤집는다 — 별도 keyframes 를 만들 필요가 없다
.marquee__row--rev .marquee__track { animation-name: marquee-scroll; animation-direction: reverse; }

.marquee__chip {
  margin-right: 12px;   // 트랙의 gap 대신 — 세트 폭이 정확히 절반이 되어 -50% 이음새가 0px 이 된다
  flex-shrink: 0;
  display: grid;
  place-items: center;
  height: 32px;
  padding: 0 14px;
  border-radius: $r-pill;
  background: $color;
  color: $stage-yellow;
  font-weight: 700; font-size: 12px; line-height: 1; font-family: inherit;
  letter-spacing: .04em;
}

@keyframes marquee-scroll {
  from { transform: translateX(0); }
  to   { transform: translateX(-50%); }
}

@media (prefers-reduced-motion: reduce) {
  .marquee__track { animation: none; transform: translateX(0); }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.marquee {
  width: min(320px, 84vw);
  display: grid;
  gap: 12px;
}

.marquee__row {
  overflow: hidden;
}

.marquee__track {
  display: flex;
  width: max-content;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

.marquee__row--fwd .marquee__track {
  animation-name: marquee-scroll;
}

.marquee__row--rev .marquee__track {
  animation-name: marquee-scroll;
  animation-direction: reverse;
}

.marquee__chip {
  margin-right: 12px;
  flex-shrink: 0;
  display: grid;
  place-items: center;
  height: 32px;
  padding: 0 14px;
  border-radius: 999px;
  background: #17141a;
  color: #ffd23f;
  font-weight: 700;
  font-size: 12px;
  line-height: 1;
  font-family: inherit;
  letter-spacing: 0.04em;
}

@keyframes marquee-scroll {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(-50%);
  }
}
@media (prefers-reduced-motion: reduce) {
  .marquee__track {
    animation: none;
    transform: translateX(0);
  }
}

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

export type DualDirectionMarqueeProps = {
  forward?: string[];
  reverse?: string[];
  duration?: number;
  easing?: string;
  color?: string;
};

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

function Row({ items, reverse }: { items: string[]; reverse?: boolean }) {
  return (
    <div className={styles.row}>
      <div className={reverse ? `${styles.track} ${styles.reverse}` : styles.track}>
        {items.map((it) => (
          <span key={it} className={styles.chip}>{it}</span>
        ))}
        {items.map((it) => (
          <span key={"dup-" + it} className={styles.chip} aria-hidden="true">{it}</span>
        ))}
      </div>
    </div>
  );
}

export default function DualDirectionMarquee({
  forward = ["DESIGN", "MOTION", "LAYOUT"],
  reverse = ["CSS", "SCSS", "REACT"],
  duration = 12000,
  easing = "linear",
  color = "#17141a",
}: DualDirectionMarqueeProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.marquee} style={vars}>
      <Row items={forward} />
      <Row items={reverse} reverse />
    </div>
  );
}