body {

  margin: 0;
  padding: 0;
  background-color: #F3F3F3;
  scroll-behavior: smooth;
}

.hidden-o {
  opacity: 0;
  transition: opacity .6s ease-in-out;
}

.visible-o {
  opacity: 1;
  transition: opacity .2s ease-in-out;
}

#hiddenheader {
  display: none;
}