01Nút lún xuống khi nhấn

<main class="stage">
  <button class="btn is-demo" type="button">Gửi</button>
</main>

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

// ── 변수 3개. 변형은 이것만 바꾼다 ──────────────────────────
$duration: $dur-quick;                             // 눌렸다 돌아오는 시간
$easing: $ease-spring;                             // 처음 빠르고 끝은 스프링처럼
$color: $subject-blue;                             // 버튼 색

// ── 데모 무대 ──────────────────────────────────────────
@include stage($stage-ink);

.btn {
  border: 0;
  border-radius: $r-control;
  padding: clamp(14px, 5vw, 22px) clamp(28px, 9vw, 56px);
  font-weight: 700;
  font-size: clamp(15px, 4.4vw, 20px);
  line-height: 1;
  font-family: inherit;
  color: $subject-cream;
  background: $color;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  transform: scale(1);
  box-shadow: $shadow-raised;
  transition: transform $duration $easing, box-shadow $duration $easing;

  &:active {
    transform: scale(.96);
    box-shadow: $shadow-press;
  }

  // 데모 · 문서용: 스스로 눌렸다 돌아오길 2초마다 반복한다
  &.is-demo {
    animation: press-loop $dur-loop $easing infinite;
  }
}

@keyframes press-loop {
  0%, 12%  { transform: scale(1); box-shadow: $shadow-raised; }
  22%      { transform: scale(.96); box-shadow: $shadow-press; }
  38%, 100% { transform: scale(1); box-shadow: $shadow-raised; }
}

// ── 접근성: 움직임 줄이기 설정이면 순간 전환만 ────────────
@media (prefers-reduced-motion: reduce) {
  .btn { transition: none; }
  .btn.is-demo { animation: none; }
  .btn:active { transform: none; box-shadow: $shadow-press; }
}

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);
}

.btn {
  border: 0;
  border-radius: 12px;
  padding: clamp(14px, 5vw, 22px) clamp(28px, 9vw, 56px);
  font-weight: 700;
  font-size: clamp(15px, 4.4vw, 20px);
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
  background: #2f6df6;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  transform: scale(1);
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1), box-shadow 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}
.btn:active {
  transform: scale(0.96);
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}
.btn.is-demo {
  animation: press-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes press-loop {
  0%, 12% {
    transform: scale(1);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
  22% {
    transform: scale(0.96);
    box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  }
  38%, 100% {
    transform: scale(1);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
}
@media (prefers-reduced-motion: reduce) {
  .btn {
    transition: none;
  }
  .btn.is-demo {
    animation: none;
  }
  .btn:active {
    transform: none;
    box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  }
}

// 실제 클릭에선 :active 만으로 눌림이 즉시 반응한다. 데모(.is-demo)는 손을 대면 자동 루프를 멈춘다.
document.querySelector('.btn').addEventListener('pointerdown', function (e) {
  e.currentTarget.classList.remove('is-demo');
});

import type { CSSProperties, MouseEvent, ReactNode } from "react";
import styles from "./PressScaleButton.module.scss";

export type PressScaleButtonProps = {
  children: ReactNode;
  /** 눌렸다 돌아오는 시간 (기본 220ms) */
  duration?: number;
  /** CSS easing (기본 스프링) */
  easing?: string;
  /** 버튼 색 */
  color?: string;
  onClick?: (e: MouseEvent<HTMLButtonElement>) => void;
  type?: "button" | "submit";
  className?: string;
};

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

export default function PressScaleButton({
  children,
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
  onClick,
  type = "button",
  className = "",
}: PressScaleButtonProps) {
  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
  };

  return (
    <button type={type} className={`${styles.btn} ${className}`} style={vars} onClick={onClick}>
      {children}
    </button>
  );
}