.calculator{width:80%;margin:0 auto;padding:10px}h2{text-align:center}.input-group{margin-bottom:10px}label{display:block;color:#666;margin-bottom:5px;font-size:14px;font-weight:700}input[type="number"]{padding:10px;width:100%;border:1px solid #ccc;border-radius:4px;font-size:14px}button{padding:10px 20px;background-color:#4CAF50;color:#fff;border:none;border-radius:4px;font-size:14px;font-weight:700;cursor:pointer}#result{background-color:#f5f5f5;padding:10px;margin-top:20px;text-align:center}