09フォーカスリングアニメーション

<main class="stage">
  <div class="field">
    <label class="field__label" for="name">名前</label>
    <input class="field__input is-demo" id="name" type="text" placeholder="名前">
  </div>
</main>

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

$duration: $dur-quick;                                  // 실제 포커스 시 링이 벌어지는 시간
$easing: $ease-out;
$color: $subject-blue;                                  // 링 색

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

.field { width: min(220px, 70vw); }
.field__label {
  display: block;
  margin-bottom: 6px;
  font-weight: 600; font-size: clamp(11px, 3vw, 12px); line-height: 1.3; font-family: inherit;
  color: rgba($subject-cream, .7);
}
.field__input {
  box-sizing: border-box;
  width: 100%;
  border: 2px solid rgba($subject-cream, .3);
  border-radius: $r-control;
  padding: 12px 14px;
  font-weight: 500; font-size: clamp(13px, 3.6vw, 15px); line-height: 1.3; font-family: inherit;
  color: $subject-cream;
  background: transparent;
  outline: 2px solid transparent;
  outline-offset: 0;
  transition: outline-color $duration $easing, outline-offset $duration $easing;
}
.field__input:focus-visible { outline-color: $color; outline-offset: 4px; }

// 데모 루프: 링이 붙어 있다가 튀어나오듯 벌어지고 다시 붙는다
.field__input.is-demo { animation: ring $dur-loop $easing infinite; }
@keyframes ring {
  0%, 10%  { outline-offset: 0; outline-color: rgba($color, .9); }
  45%, 65% { outline-offset: 4px; outline-color: rgba($color, .2); }
  100%     { outline-offset: 0; outline-color: rgba($color, .9); }
}

@media (prefers-reduced-motion: reduce) {
  .field__input { transition: none; }
  .field__input.is-demo { animation: none; outline-color: rgba($color, .9); }
}

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);
}

.field {
  width: min(220px, 70vw);
}

.field__label {
  display: block;
  margin-bottom: 6px;
  font-weight: 600;
  font-size: clamp(11px, 3vw, 12px);
  line-height: 1.3;
  font-family: inherit;
  color: rgba(255, 247, 230, 0.7);
}

.field__input {
  box-sizing: border-box;
  width: 100%;
  border: 2px solid rgba(255, 247, 230, 0.3);
  border-radius: 12px;
  padding: 12px 14px;
  font-weight: 500;
  font-size: clamp(13px, 3.6vw, 15px);
  line-height: 1.3;
  font-family: inherit;
  color: #fff7e6;
  background: transparent;
  outline: 2px solid transparent;
  outline-offset: 0;
  transition: outline-color 220ms ease-out, outline-offset 220ms ease-out;
}

.field__input:focus-visible {
  outline-color: #2f6df6;
  outline-offset: 4px;
}

.field__input.is-demo {
  animation: ring 2s ease-out infinite;
}

@keyframes ring {
  0%, 10% {
    outline-offset: 0;
    outline-color: rgba(47, 109, 246, 0.9);
  }
  45%, 65% {
    outline-offset: 4px;
    outline-color: rgba(47, 109, 246, 0.2);
  }
  100% {
    outline-offset: 0;
    outline-color: rgba(47, 109, 246, 0.9);
  }
}
@media (prefers-reduced-motion: reduce) {
  .field__input {
    transition: none;
  }
  .field__input.is-demo {
    animation: none;
    outline-color: rgba(47, 109, 246, 0.9);
  }
}

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

export type FocusRingFieldProps = {
  label: string;
  placeholder: string;
  /** 실제 포커스 시 링이 벌어지는 시간 (기본 220ms) */
  duration?: number;
  easing?: string;
  /** 링 색 */
  color?: string;
};

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

export default function FocusRingField({
  label,
  placeholder,
  duration = 220,
  easing = "ease-out",
  color = "#2f6df6",
}: FocusRingFieldProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const id = "focus-" + label.replace(/\s+/g, "-").toLowerCase();

  return (
    <div className={styles.field} style={vars}>
      <label className={styles.label} htmlFor={id}>{label}</label>
      <input className={styles.input} id={id} type="text" placeholder={placeholder} />
    </div>
  );
}