#menubtns {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  }
  
  #menubtns button {
    width: 300px;
    height: 80px;
    font-size: 40px;
  }