body {
  line-height: 140%;
  margin: 50px;
  width: 650px;
}

code {
  font-size: 14px;
  text-align: left;
  background-color: #eee;
  display: block;
  padding: 10px;
}

.container {
  display: flex;
}

.fixed {
  width: 400px;
}

.flex-item {
  flex-grow: 1;
}