赤いカプセル型グラデーションボタン

<a href="#" class="round-btn">ボタン</a>

.round-btn {
  display: inline-block;
  font-family: 'Arial', sans-serif;
  font-size: 18px;
  font-weight: bold;
  letter-spacing: 1px;
  color: #fff;
  text-decoration: none;
  background: linear-gradient(#f3816e, #e53935);
  padding: 14px 36px;
  border-radius: 50px;
  position: relative;
  box-shadow: 0 4px 6px rgba(0,0,0,0.2);
  transition: 0.2s ease;
}

/* ホバー時の色変化 */
.round-btn:hover {
  background: linear-gradient(#f88b79, #ef5350);
  box-shadow: 0 6px 10px rgba(0,0,0,0.25);
}