body, html {
  margin: 0;
  padding: 0;
}

main {
  width: 890px;
  margin: auto;

  font-family: sans-serif;
}

.intro {
  background: white;
  position: sticky;
  top: 0;
  z-index: 20p;
  padding: 20px;
  border-bottom: 1px solid lightgray;
}