button {
    margin: 3px;
  }

  button:hover {
    cursor: pointer;
  }

  #first-num,
  #second-num {
    width: 60px;
  }

  output {
    border: 1px solid gray;
    display: block;
    height: 18px;
    margin-top: 5px;
    padding: 5px;
    width: 240px;
  }

  main {
    width: 528px;
  }

  #error-btns {
    column-gap: 5px;
    display: flex;
    flex-wrap: wrap;
    margin-top: 30px;
    row-gap: 5px;
  }

  #error-btns>* {
    padding: 8px 2px;
    width: 122px;
  }