nav li:nth-child(1) {
  background-color: #00b7b5;
}

.header {
  color: #02075d;
  background-color: lightblue;
  text-align: center;
  font-size: 32px;
  padding: 5px;
}

main img {
  max-width: 100%;
  margin-bottom: 20px;
}