function main() {
  const path=$data.history.map(p=>p.latitude===null||p.longitude===null
    ? null:{latitude:p.latitude,longitude:p.longitude});
  const valid=path.filter(p=>p!==null).length;
  return <CardContent title="最近 30 秒路线" trailing={valid+' 点'}
    fulled={true} headerBlurColor="clear">
    <Map width="fill" height="fill" followMode={MapFollowMode.latestData}
      path={path} pathStyle={MapPathStyle.arrow}
      pathWidth={4} pathColor={$env.accent}
      pathOutlineWidth={1} pathOutlineColor={$env.dark?'#18201C':'#FFFFFF'}/>
  </CardContent>;
}