body {
  font-family: sans-serif;
  background: #f9f9f9;
  color: #333;
  line-height: 1.6;
  padding: 20px;
}
header {
  background: #282c34;
  color: #fff;
  padding: 20px;
  text-align: center;
}
.btn {
  display: inline-block;
  padding: 10px 15px;
  background: #f60;
  color: #fff;
  text-decoration: none;
  border-radius: 5px;
}
section {
  margin: 20px 0;
}
footer {
  text-align: center;
  margin-top: 40px;
  font-size: 0.9em;
  color: #666;
}