.btn-ios {
      background-color: #000;
      color: #fff;
    }

    .btn-android {
      background-color: #3DDC84;
      color: #fff;
    }

    .btn-windows {
      background-color: #0078D7;
      color: #fff;
    }

    .btn-ios:hover {
      background-color: #333;
    }

    .btn-android:hover {
      background-color: #2FA769;
    }

    .btn-windows:hover {
      background-color: #005EA6;
    }