function main() {
  const reading = $data.current;
  const speed = reading.speed;
  return <CardContent title="速度">
    <VStack spacing={6}>
      <Text fontSize={64} fontWeight="light" fontDesign="rounded"
        minimumScaleFactor={0.5} color={$env.foreground}
        contentAnimation={{type: 'numericText'}}>
        {speed === null ? '—' : Math.round(speed)}
      </Text>
      <Text fontSize={12} color={$env.accent}>{reading.speedUnit}</Text>
    </VStack>
  </CardContent>;
}