body {
      background-color: black;
      color: white;
      /* comment: color means font color */
      font-family: "arial";

      margin: 100px 200px;
      /* margin: top-bottom left right */
      /* can use % 10% 20% */
    }
    a {
      color: yellow;
    }

    ol{

      list-style-type: upper-roman;
    }

    button{
  border-color: dimgray;
  background-color: grey;
  color: white;
  box-shadow: 0 0 5px rgba(0, 0, 0, 1.0);
  cursor: pointer;
}