.calculator{max-width:400px;text-align:center;margin:0 auto;padding:20px;background-color:#fff;border-radius:5px;box-shadow:0 0 10px rgba(0,0,0,.2)}.calculator .input-group{margin:10px 0}.calculator label{display:inline-block;width:120px;text-align:right;margin-right:10px}.calculator input{width:60px;padding:5px}.calculator button{padding:10px 20px;color:#fff;border:none;border-radius:5px;cursor:pointer}.result{margin-top:20px;font-weight:700}