* {
    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;
  }