body{margin:0;font-family:Arial,sans-serif;background:#f4f6f9;display:flex;justify-content:center;align-items:center;height:100vh}.calculator{background:#fff;padding:30px;border-radius:12px;box-shadow:0 4px 20px #0000001a;width:100%;max-width:400px;display:flex;flex-direction:column;gap:15px}input,select,button{padding:10px;font-size:16px}button{background:#2563eb;color:#fff;border:none;cursor:pointer;border-radius:6px}button:hover{background:#1e40af}.error{color:red}@media(max-width:768px){.calculator{max-width:90%}}@media(max-width:480px){.calculator{padding:20px}}