html {
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  background:linear-gradient(0deg, rgba(0, 0, 0, 0.6), rgba(0, 0, 0, 0.6)), url(/images/zero-backgroup.jpg);
  background-size: cover;
}
body {
  margin: 0;
  min-height: 100%;
  font-family: 'Orbitron', sans-serif;
  color: #fff;
  background-size: cover;
  display: flex;
  flex-direction: column;
}

header {
  background-color: rgba(20, 20, 20, 0.85);
  padding: 1rem;
  text-align: center;
}

nav {
  display: flex;
  justify-content: center;
  background-color: rgba(30, 30, 30, 0.85);
  flex-wrap: wrap;
}

nav a {
  color: #00ffff;
  text-decoration: none;
  padding: 1rem;
  transition: background 0.3s;
}

nav a:hover {
  background-color: rgba(0, 255, 255, 0.2);
}

a, a:hover, a:active, a:visited { color: white; }

/* Let main content grow to fill space */
main {
  flex: 1;
  padding: 2rem;
  text-align: center;
}

section {
  margin-bottom: 2rem;
}

/* Footer stays at bottom */
footer {
  background-color: rgba(20, 20, 20, 0.85);
  text-align: center;
  padding: 1rem;
}

@media (max-width: 600px) {
  nav a {
    flex: 1 1 100%;
    text-align: center;
  }
}

.content {
  flex: 1;
}