:root{--bg:#f6f9fc;--card:#fff;--text:#1f2937;--primary:#4a90e2;--muted:#6b7280}[data-theme=dark]{--bg:#0f172a;--card:#1e293b;--text:#f8fafc;--muted:#9ca3af}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font-family:system-ui,-apple-system,BlinkMacSystemFont,sans-serif}.container{max-width:720px;margin:auto;padding:16px}.card{background:var(--card);padding:14px;margin-bottom:14px}.card,button{border-radius:14px}button{width:100%;padding:16px;font-size:1rem;border:none;background:var(--primary);color:#fff}