body {
  background: #7C2121;
}

.container {
  padding: 20px 0;
  width: 309px;
}

.calculator {
  background: #777;
  border-radius: 3px;
  box-shadow: 0 0 5px rgba(0,0,0,0.8);
  padding: 10px 7px 7px 10px;
}

  .calculator li {
    background: #c7c7c7;
    cursor: pointer;
    float: left;
    margin: 0 3px 3px 0;
    text-align: center;
    width: 70px;
    height: 40px;
    line-height: 40px;
  }

  .calculator li:hover {
    background: #a3a3a3;
  }

  li.op {
    background: #333;
    color: #e3e3e3;
  }

  li.op:hover {
    background: #555;
  }

  li.result,
  li.result:hover,
  li.enter {
    background: #000;
    color: #FFF;
    padding: 0 20px;
    width: 289px;
  }

  li.result {
    border-radius: 3px 3px 0 0;
    cursor: default;
    text-align: right;
  }

  li.enter {
    border-radius: 0 0 3px 3px;
  }

  li.enter:hover {
    background: #333;
  }