/* [OVERLAY] */
#overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100vh;
  background: rgba(0, 0, 0, 0.8);
  z-index: 999;
  /* We hide the overlay by default */
  visibility: hidden;
  opacity: 0;
  transition: all 0.5s;
}
/* This CSS class will show the overlay */
#overlay.show {
  visibility: visible;
  opacity: 1;
}

/* [OVERLAY TEXT] */
#o-text {
  margin: 10% auto 0 auto;
  max-width: 30%;
  z-index: 1000;
  padding: 10px;
  background: #fff;
  text-align: center;
  font-size: 2em;
}

/* [OVERLAY CLOSE BUTTON] */
#o-close {
  position: absolute;
  top: 15%;
  right: 5px;
  color: #fff;
  font-size: 3em;
  cursor: pointer;
  z-index: 1000;
}

/* [FILL] */
html, body {
  padding: 0;
  margin: 0;
}

/* [DOES NOT MATTER] */
html, body {
  font-family: arial, sans-serif;
}