01대각선 하이라이트 스윕 보더

<main class="stage">
  <div class="frame is-demo">
    <input class="frame__input" type="text" placeholder="메시지를 입력하세요" readonly>
  </div>
</main>

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

$duration: $dur-loop;                                  // 줄무늬가 한 바퀴 흐르는 시간
$easing: linear;                                        // 흐름은 일정 속도로
$color: $subject-blue;                                  // 줄무늬 색

@include stage($stage-ink);
.stage { padding: clamp(6px, 2.4vw, 16px); }

.frame {
  position: relative;
  width: min(230px, 74vw);
  border-radius: $r-control;
  padding: 3px;
  isolation: isolate;
}

// 테두리 자리에만 보이게 잘라낸 링 위에 대각선 줄무늬를 흘려보낸다
.frame::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: $r-control;
  padding: 3px;
  background: repeating-linear-gradient(115deg, $color 0 10px, $subject-cream 10px 14px, transparent 14px 34px);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;                          // 옛 사파리
  mask-composite: exclude;                              // 표준 (mask 무접두사 지원표: blog-topic 편브리프)
}
.frame.is-demo::before,
.frame:focus-within::before { animation: sweep $duration $easing infinite; }

.frame__input {
  position: relative;
  display: block;
  box-sizing: border-box;
  width: 100%;
  border: 0;
  border-radius: $r-control - 3px;
  padding: 14px 16px;
  font-weight: 500; font-size: clamp(13px, 3.6vw, 15px); line-height: 1.3; font-family: inherit;
  color: $subject-cream;
  background: $stage-ink;
}
.frame__input::placeholder { color: rgba($subject-cream, .55); }

@keyframes sweep { to { background-position: 220px 0; } }

@media (prefers-reduced-motion: reduce) {
  .frame.is-demo::before, .frame:focus-within::before { animation: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.stage {
  padding: clamp(6px, 2.4vw, 16px);
}

.frame {
  position: relative;
  width: min(230px, 74vw);
  border-radius: 12px;
  padding: 3px;
  isolation: isolate;
}

.frame::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 12px;
  padding: 3px;
  background: repeating-linear-gradient(115deg, #2f6df6 0 10px, #fff7e6 10px 14px, transparent 14px 34px);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
}

.frame.is-demo::before,
.frame:focus-within::before {
  animation: sweep 2s linear infinite;
}

.frame__input {
  position: relative;
  display: block;
  box-sizing: border-box;
  width: 100%;
  border: 0;
  border-radius: 9px;
  padding: 14px 16px;
  font-weight: 500;
  font-size: clamp(13px, 3.6vw, 15px);
  line-height: 1.3;
  font-family: inherit;
  color: #fff7e6;
  background: #17141a;
}

.frame__input::placeholder {
  color: rgba(255, 247, 230, 0.55);
}

@keyframes sweep {
  to {
    background-position: 220px 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .frame.is-demo::before, .frame:focus-within::before {
    animation: none;
  }
}

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

export type SweepBorderInputProps = {
  placeholder: string;
  /** 줄무늬가 한 바퀴 흐르는 시간 (기본 2000ms) */
  duration?: number;
  easing?: string;
  /** 줄무늬 색 */
  color?: string;
};

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

export default function SweepBorderInput({
  placeholder,
  duration = 2000,
  easing = "linear",
  color = "#2f6df6",
}: SweepBorderInputProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.frame} style={vars}>
      <input className={styles.input} type="text" placeholder={placeholder} readOnly />
    </div>
  );
}