07押し込みの反動（スクワッシュ）

<main class="stage">
  <button class="squash is-demo" type="button"><span class="squash__label">送信する</span></button>
</main>

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

// 변형은 이 세 줄만 바꾼다
$duration: $dur-loop;
$easing:   $ease-pop;
$color:    $subject-pink;

@include stage($stage-yellow);

.squash {
  border: 0;
  cursor: pointer;
  padding: $sp-4 $sp-10;
  border-radius: $r-control;
  background: $color;
  color: $subject-ink;
  font-family: inherit;
  font-size: clamp(17px, 5vw, 22px);
  font-weight: 800;
  box-shadow: $shadow-raised;
  transform-origin: center bottom;
}

.squash.is-demo { animation: squash-press $duration $easing infinite; }

// 눌림(scale 1.06/.88) → 반동(.97/1.06) → 안착. 100% 가 0% 와 같은 값이라 되감기가 없다
@keyframes squash-press {
  0%,  34% { transform: scale(1, 1);       box-shadow: $shadow-raised; }
  46%      { transform: scale(1.06, .88);  box-shadow: $shadow-press; }
  60%      { transform: scale(.97, 1.06);  box-shadow: $shadow-raised; }
  72%      { transform: scale(1.02, .98);  box-shadow: $shadow-raised; }
  86%, 100% { transform: scale(1, 1);      box-shadow: $shadow-raised; }
}

// 손으로 눌렀을 때도 같은 눌림 값
.squash:active {
  animation: none;
  transform: scale(1.06, .88);
  box-shadow: $shadow-press;
}

@media (prefers-reduced-motion: reduce) {
  .squash.is-demo { animation: none; }
  .squash:active { transform: none; }
}

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);
}

.squash {
  border: 0;
  cursor: pointer;
  padding: 16px 40px;
  border-radius: 12px;
  background: #ff9ebb;
  color: #17141a;
  font-family: inherit;
  font-size: clamp(17px, 5vw, 22px);
  font-weight: 800;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transform-origin: center bottom;
}

.squash.is-demo {
  animation: squash-press 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
}

@keyframes squash-press {
  0%, 34% {
    transform: scale(1, 1);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
  46% {
    transform: scale(1.06, 0.88);
    box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  }
  60% {
    transform: scale(0.97, 1.06);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
  72% {
    transform: scale(1.02, 0.98);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
  86%, 100% {
    transform: scale(1, 1);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
}
.squash:active {
  animation: none;
  transform: scale(1.06, 0.88);
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}

@media (prefers-reduced-motion: reduce) {
  .squash.is-demo {
    animation: none;
  }
  .squash:active {
    transform: none;
  }
}

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

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

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

export default function SquashPressButton({
  label = "Submit",
  duration = 2000,
  easing = "cubic-bezier(.2,1.4,.4,1)",
  color = "#ff9ebb",
}: SquashPressButtonProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <button type="button" className={styles.squash} style={vars}>
      {label}
    </button>
  );
}