* {
  box-sizing: border-box;
}

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

body {
  font-family: Arial, Helvetica, sans-serif;
  font-size: 13px;
  display: flex;
}

body > main {
  flex: 1;
  display: flex;
  flex-direction: column;
}