html, body,
body > header,
body > section.tester-container {
  margin: 0;
  padding: 0;
}
html, body {
  background-color: white;
  font-family: sans-serif;
  font-size: 12px;
  box-sizing: border-box;
}
body > header,
body > section.tester-container {
  display: block;
  padding: 1rem;
  text-align: center;
}

body > header > a {
  text-decoration: none;
}
body > header > a > h1 {
  display: inline-block;
  color: #ed2324;
  font-size: 2rem;
  margin: 0;
}