nav {
  text-align: center;
  a {
    padding: 0 20px;
  }
}

@media screen and (min-width: 800px) {
  .flex-container {
    display: flex;
    flex-wrap: wrap;
  }
  .sidebar {
    width: 20%;
  }
  .main {
    width: 80%;
  }
  nav {
    position: fixed;
    top: 70px;
    left: 15%;
    a {
      display: block;
      padding: 20px 0;
    }
  }
}

nav {
  text-align: center;
  a {
    padding: 0 10px;
  }
}

@media screen and (min-width: 400px) {
  nav {
    a {
      padding: 0 20px;
    }
  }
}

@media screen and (min-width: 800px) {
  .flex-container {
    display: flex;
    flex-wrap: wrap;
  }
  .sidebar {
    width: 20%;
  }
  .main {
    width: 80%;
  }
  nav {
    position: fixed;
    top: 70px;
    left: 15%;
    a {
      display: block;
      padding: 20px 0;
    }
  }
}

Fix the nav padding on small devices
Fix the nav padding on small devices
