*, :after, :before{
  box-sizing:border-box;
}

html, body, main {
  margin: 0;
  width: 100%;
  height: 100%;
}

body {
  margin: 16px;
  width: calc(100% - 32px);
  height: calc(100% - 32px);
}

main {
  display: block;
}