body {
  background: url(https://www.nasa.gov/sites/default/files/styles/full_width/public/thumbnails/image/main_image_star-forming_region_carina_nircam_final-1280.jpg?itok=9hyNVMwe);
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
  font-family: Arial, sans-serif;

}

html,
body,
#main {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
}

#main {
  background: rgba(0, 0, 0, 0.85);
}

#center {
  margin: 0;
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 100%;
  text-align: center;
}

h1 {
  color: #EEE;
  font-size: 40pt;
  margin: 0;
}

.button {
  background-color: #1f74de;
  display: inline-block;
  padding: 10pt;
  margin: 0 2.5pt;
  border-radius: 3pt;
  color: #FFF;
  width: 150pt;
  text-decoration: none;
  text-transform: uppercase;
  font-weight: bold;
  transition: background-color 0.2s ease-in-out;
}

p {
  margin: 0;
  margin-top: 10pt;
  margin-bottom: 15pt;

  color: #BBB;
}

.button:hover {
  background-color: #1355a8;
}

footer {
  color: #FFF;
  position: absolute;
  bottom: 0;
  width: 100%;
  padding: 0;
  text-align: center;
}

.button img{
  filter: invert(100%) sepia(7%) saturate(7477%) hue-rotate(290deg) brightness(113%) contrast(107%);
  display: inline-block;
  width: 1.5em;
  vertical-align: middle; /* added */

}

footer a:link,
footer a:visited,
footer a:hover,
footer a:focus,
footer a:active,
footer a:visited:hover,
footer a:visited:focus,
footer a:visited:active {
  color: #FFF;
}