@media screen and (max-width: 700px) {
  .row {
    flex-direction: column;
  }
}
@media screen and (max-width: 400px) {
  .navbar a {
    float: none;
    width: 100%;
  }
}

body {
  font-family: sans-serif;
}
a {
  color: blue;
}

.header {
  padding: 10px;
  text-align: center;
  background: #4FA2F5;
  color: white;
}
.header h1 {
  font-size: 40px;
}

.navbar {
  overflow: hidden;
  background-color: #999;
}
.navbar a {
  float: left;
  display: block;
  color: white;
  text-align: center;
  padding: 14px 20px;
  text-decoration: none;
}
/* .navbar a.right {
  float: right;
} */
.navbar a:hover {
  background-color: #ddd;
  color: black;
}

* {
  box-sizing: border-box;
}
.row {
  display: flex;
  flex-wrap: wrap;
}
.side {
  flex: 25%;
  background-color: lightgray;
  padding: 20px;
}
.main {
  flex: 70%;
  background-color: white;
  padding: 20px;
  max-width: 650px;
}
.footer {
  padding: 20px;
  text-align: center;
  background: #ddd;
}

@media (prefers-color-scheme: dark) {
  body {
    background-color: black;
  }
  a {
    color: #4da6ff;
  }
  .header {
    background: #1A406B;
    color: lightgray;
  }
  .navbar {
    background-color: #222;
  }
  .navbar a {
    color: lightgray;
  }
  .navbar a:hover {
    background-color: #444;
    color: white;
  }
  .side {
    background-color: #111;
    color: lightgray;
  }
  .main {
    background-color: black;
    color: lightgray;
  }
  .footer {
    background: #222;
    color: lightgray;
  }
  max-width: 650px;
}