* {
  font-family: Arial, Helvetica, sans-serif;
}

html, body {
  margin: 0;
  border: 0;
  padding: 0;
  background-color: #fff;
}

main {
  margin: auto;
  width: 50%;
  padding: 20px;
}

main > h1 {
  text-align: center;
  font-size: 3.5em;
}
body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

header {
  background-color: #333;
  color: #fff;
  padding: 1rem 0;
}

nav ul {
  list-style: none;
  display: flex;
  justify-content: center;
  padding: 0;
}

nav ul li {
  margin: 0 1rem;
}

nav ul li a {
  color: #fff;
  text-decoration: none;
}

main {
  padding: 2rem;
  text-align: center;
}

section {
  margin: 2rem 0;
}

.btn {
  display: inline-block;
  padding: 0.5rem 1rem;
  background-color: #007BFF;
  color: #fff;
  text-decoration: none;
  border-radius: 5px;
}

footer {
  background-color: #333;
  color: #fff;
  text-align: center;
  padding: 1rem 0;
  position: fixed;
  width: 100%;
  bottom: 0;
}