#hello_menu_center {  }

.hello_menu_center_item { text-align:center; }
.hello_menu_center_button {
  width: 16em;
  display: block;
  display: inline-block;
  text-decoration: none;
  font-size: 2em;
  padding: .5em;
  margin: .4em;
  background: #77f;
  color: #fff;
  border: solid .1em #ccf;
  cursor: pointer;
}
.hello_menu_center_button:hover {
  background: #fa0;
  color: #ff0;
  border-color: #ea0;
}


@media (orientation: portrait) {

  .hello_menu_center_button {
    width: 90%;
    font-size: 4em;
    padding: 1em 1%;
    margin: .1em 1%;
  }

}