body {
  font-family: sans-serif;
  margin: 0;
}

nav {
  background: #333;
}

nav ul {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

nav li {
  flex: 1;
}

nav button {
  width: 100%;
  padding: 14px;
  border: none;
  background: #333;
  color: white;
  font-size: 16px;
  cursor: pointer;
}

nav button:hover {
  background: #555;
}

main {
  padding: 20px;
}

.prewrap {
  white-space: pre-wrap;
  font-family: monospace;
  background: #f4f4f4;
  padding: 10px;
  border-radius: 4px;
}