ブクッとふくらむポップボタン

<div class="push-button_box">
  <a href="#" class="push-button pop-bounce">はじめる！</a>
</div>

.push-button_box {
  width: 30%;
  margin: 50px auto;
}

.push-button.pop-bounce {
  display: block;
  width: 100%;
  padding: 16px 0;
  background: #f87171;
  color: #fff;
  font-weight: bold;
  font-size: 16px;
  text-align: center;
  border-radius: 999px;
  text-decoration: none;
  box-shadow: 0 6px 0 #b91c1c;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.push-button.pop-bounce:hover {
  transform: scale(1.05) translateY(-3px);
  box-shadow: 0 8px 0 #991b1b;
}