01左右に揺れる

<main class="stage">
  <div class="sh is-demo">
    <label class="sh__label" for="sh-email">メール</label>
    <input class="sh__input" id="sh-email" type="email" value="wrong@mail" aria-invalid="true" readonly>
    <p class="sh__msg">正しいメール形式ではありません</p>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 500ms;                                 // 흔들림 한 번의 길이
$easing: $ease-out;
$color: $error;                                    // 오류 테두리·문구 색

@include stage($stage-ink);

.sh { width: min(260px, 86vw); display: flex; flex-direction: column; gap: $sp-2; }
.sh__label { font-weight: 600; font-size: 12px; line-height: 1; font-family: inherit; color: $subject-cream; }
.sh__input {
  box-sizing: border-box;
  width: 100%;
  padding: $sp-2 $sp-3;
  border-radius: $r-sm;
  border: 2px solid $color;
  background: rgba(255, 255, 255, .06);
  color: $subject-cream;
  font-weight: 400;
  font-size: 14px;
  line-height: 1;
  font-family: inherit;
}
.sh__msg { margin: 0; color: $error-soft; font-weight: 500; font-size: 11px; line-height: 1.3; font-family: inherit; }

// 실제 동작: 폼 검증에 실패해 .sh--invalid 가 붙으면 한 번만 흔들린다 (JS 없이 클래스 하나로 충분)
@keyframes sh-shake {
  0%, 22%, 100% { transform: translateX(0); }
  2%  { transform: translateX(-7px); }
  4%  { transform: translateX(7px); }
  6%  { transform: translateX(-7px); }
  8%  { transform: translateX(7px); }
  10% { transform: translateX(-5px); }
  12% { transform: translateX(5px); }
  14% { transform: translateX(-3px); }
  16% { transform: translateX(3px); }
  18% { transform: translateX(-1px); }
  20% { transform: translateX(1px); }
}
.sh__input.sh--invalid { animation: sh-shake $duration $easing; }

// 데모 루프: 클릭 전까지 계속 흔들려 무엇이 움직이는지 보여준다
.sh.is-demo .sh__input { animation: sh-shake $duration $easing infinite; }

// ── 접근성 ──────────────────────────────────────────
@media (prefers-reduced-motion: reduce) {
  .sh__input.sh--invalid,
  .sh.is-demo .sh__input { animation: none !important; }
}

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);
}

.sh {
  width: min(260px, 86vw);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.sh__label {
  font-weight: 600;
  font-size: 12px;
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
}

.sh__input {
  box-sizing: border-box;
  width: 100%;
  padding: 8px 12px;
  border-radius: 8px;
  border: 2px solid #c2361a;
  background: rgba(255, 255, 255, 0.06);
  color: #fff7e6;
  font-weight: 400;
  font-size: 14px;
  line-height: 1;
  font-family: inherit;
}

.sh__msg {
  margin: 0;
  color: #ffe0d8;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.3;
  font-family: inherit;
}

@keyframes sh-shake {
  0%, 22%, 100% {
    transform: translateX(0);
  }
  2% {
    transform: translateX(-7px);
  }
  4% {
    transform: translateX(7px);
  }
  6% {
    transform: translateX(-7px);
  }
  8% {
    transform: translateX(7px);
  }
  10% {
    transform: translateX(-5px);
  }
  12% {
    transform: translateX(5px);
  }
  14% {
    transform: translateX(-3px);
  }
  16% {
    transform: translateX(3px);
  }
  18% {
    transform: translateX(-1px);
  }
  20% {
    transform: translateX(1px);
  }
}
.sh__input.sh--invalid {
  animation: sh-shake 500ms ease-out;
}

.sh.is-demo .sh__input {
  animation: sh-shake 500ms ease-out infinite;
}

@media (prefers-reduced-motion: reduce) {
  .sh__input.sh--invalid,
  .sh.is-demo .sh__input {
    animation: none !important;
  }
}

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

export type ShakeHorizontalProps = {
  duration?: number;
  easing?: string;
  color?: string;
};

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

export default function ShakeHorizontal({ duration = 500, easing = "ease-out", color = "#c2361a" }: ShakeHorizontalProps) {
  const [invalid, setInvalid] = useState(true);
  const [run, setRun] = useState(0);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.sh} style={vars}>
      <label className={styles.label} htmlFor="sh-email">이메일</label>
      <input
        key={run}
        id="sh-email"
        className={`${styles.input} ${invalid ? styles.shake : ""}`}
        type="email"
        defaultValue="wrong@mail"
        readOnly
        onBlur={() => { setInvalid(true); setRun((n) => n + 1); }}
      />
      <p className={styles.msg}>올바른 이메일 형식이 아닙니다</p>
    </div>
  );
}