:root{--primary:#0d6efd}body{margin:0;font-family:Arial,Helvetica,sans-serif;background:#f8f9fa}header{background:var(--primary);color:#fff;padding:12px 20px}nav a{color:#fff;margin-right:12px;text-decoration:none}.container{padding:16px}.card{background:#fff;border-radius:8px;padding:16px;box-shadow:0 2px 8px #0000000f}.input{padding:8px;margin:6px 0;width:100%}.btn{background:var(--primary);color:#fff;border:0;padding:8px 12px;border-radius:6px;cursor:pointer}.btn:disabled{opacity:.6;cursor:not-allowed}