/* Reset margins, paddings, and center text globally */
* {
    margin: 0;
    padding: 0;
    text-align: center;
  }
  
  body {
    background-color: #444;
    color: #fff;
  }
  
  span {
    border: none;
    border-top: 1px solid #222;
    border-left: 1px solid #222;
    padding: 20px 0;
    text-shadow: 0 1px 0.5px #111;
    box-shadow: inset 0 1px 0.5px rgba(255, 255, 255, 0.2),
                inset 0 -1px 0.5px rgba(1, 1, 1, 0.2);
  }
  
  .display span {
    background-color: #333;
    text-shadow: 0 2px 3px #111;
    box-shadow: none;
  }
  
  .display h1 {
    text-align: right;
    font-size: 2em;
  }
  
  .numbers span {
    background-color: #555;
  }
  
  .operations span {
    background-color: tomato;
  }
  
  .topOperations span {
    background-color: #444;
  }
  
  #equals {
    border-bottom: 1px solid #222;
    background-color: #ffb973;
  }
  
  .bb {
    border-bottom: 1px solid #222;
  }
  
  .br {
    border-right: 1px solid #222;
  }
  
  i.ai {
    color: yellow;
  }

  .logo i {
    padding: 0 3px;
  }