html, body {
  height: 100%;
  margin: 0;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  flex-shrink: 0;
}

nav {
  flex-shrink: 0;
}

.container {
  flex: 1;
}

footer {
  flex-shrink: 0;
  margin-top: auto;
  padding: 20px;
  background: #222;
  color: white;
  text-align: center;
}