body {
  margin: 0;
  background-color: black;
}
.nav {
  position: fixed;
  bottom: 0;
  width: 70%;
  margin: auto;
  left: 0;
  right: 0;
  display: flex;
  height: 6rem;
  margin-bottom: 2rem;
}
.nav-item {
  color: white;
  margin: auto;
  position: relative;
}
.nav-item img {
  width: 18rem;
}
.nav-item:hover {
  opacity: 0.7;
}

.main-body {
  height: 100%;
}

@media only screen and (max-width: 900px) {
  html {
   height: 100vh; 
  }

  .nav-item img {
    width: 16rem;
  }
}

body {
  background-color: black;
}

@media screen and (orientation:portrait) {
  html {
   height: 100vh; 
  }

  .nav {
    position: relative;
    width: fit-content;
    flex-direction: column;
  }

  .nav-item img {
    width: 32rem;
    margin-bottom: 2rem;
  }
}