fn target_cameras(
    mut commands: Commands,
    mut count: Local<usize>,
    mut query: Query<&mut TargetCamera, With<Parent>>,
) {
    *count += 1;
    if *count == 2 {
        // spawn a UI camera!
        let ui_camera = commands
            .spawn(Camera2dBundle {
                camera: Camera {
                    order: 10,
                    ..Default::default()
                },
                ..Default::default()
            })
            .id();

        for mut c in query.iter_mut() {
            c.0 = ui_camera;
        }
    }
}