@media only screen and (device-width: 320px) and (device-height: 568px)  {
  .start-btn {
    position: unset; 
   margin-top: 100px;
}

}


@media (max-device-height: 720px) {
  .start-btn {
    position: unset; 
   margin-top: 100px;
}

}