.page-not-found {
  position: fixed;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 40%;
  padding: 20px;
  text-align: center;
  box-shadow: 0 0 30px rgba(0, 0, 0, 0.2);
  text-shadow: 0 2px 1px hsla(0, 0%, 100%, .2);
}

h1 {
  font-size: 2.5em;
  margin-bottom: 0.2em;
}