html {
  background: url(images/keep-background.jpg) no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

main {
  margin: 260px auto;
  width: 50%;
  text-align: center;
}

#logo {
  width:80%;
  -webkit-filter: drop-shadow(0px 0px 10px rgba(255, 255, 255, 0.6));
         filter: drop-shadow(0px 0px 10px rgba(255, 255, 255, 0.6));
}