:root{font-family:Segoe UI,Arial,sans-serif;line-height:1.5;color:#1b1b1b;background-color:#f7f7f7}body{margin:0}.app{max-width:960px;margin:0 auto;padding:40px 24px}.panel{margin-top:24px;padding:16px;background:#fff;border-radius:8px;border:1px solid #e0e0e0}.error{color:#b00020}