body{font-family:Arial,sans-serif;background:#f5f5f5;display:flex;justify-content:center;align-items:center;min-height:100vh}.container{background:#fff;padding:20px;border-radius:8px;box-shadow:0 0 10px #0000001a;text-align:center;width:300px}input,button{width:100%;padding:8px;margin:5px 0;border:1px solid #ddd;border-radius:5px}button{background:#3498db;color:#fff;cursor:pointer}button:hover{background:#2980b9}.receipt{margin-top:20px;padding:10px;border:1px solid #ddd;text-align:left;background:#fff}.error{color:red;margin-top:10px}