html, body {
      margin: 0;
      padding: 0;
      height: 100%;
      background-color: #000;
      color: #fff;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      font-size: 14px;
      line-height: 1.5;
      display: flex;
      justify-content: center;
      align-items: center;
      text-align: center;
    }

main {
    max-width: 600px;
    padding: 20px;
}

a {
    color: #9f9;
    text-decoration: none;
    border-bottom: 1px solid #9f9;
    transition: color 0.2s ease, border-color 0.2s ease;
}

a:hover {
    color: #cfc;
    border-color: #cfc;
}