none;
      cursor: pointer;
      transition: background 0.2s, box-shadow 0.2s, transform 0.1s;
    }
    .btn:hover {
      background: #48cae4;
      box-shadow: 0 4px 16px rgba(0, 180, 216, 0.15);
    }
    .btn:active {
      background: #0096c7;
      transform: scale(0.96);
      box-shadow: 0 2px 8px rgba(0, 150, 199, 0.18);
    }
    .spinner {
      width: 48px;
      height: 48px;
      border: 5px solid #e0e0e0;
      border-top: 5px solid #00b4d8;
      border-radius: 50%;
      animation: spin