.bg_pattern {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
}
.bg_diagonal {
  opacity: 0.7;
  background: repeating-linear-gradient( 45deg, #202020, #202020 10px, #000000 10px, #000000 50px );
  z-index: -1;
}
.bg_base {
  background-image: url("../img/network.jpg");
  background-repeat: no-repeat;
  background-size: cover;
  z-index: -2;
}