bevy-playground/src/camera.rs

use bevy::prelude::*;
use bevy::render::camera::Camera as BevyCamera;

pub struct CameraPlugin;

#[derive(Component, Debug)]
pub struct CameraTarget;

impl Plugin for CameraPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, spawn)
            .add_systems(PostUpdate, follow);
    }
}

fn spawn(mut commands: Commands) {
    let mut bundle = (Camera2dBundle::default(), IsDefaultUiCamera);
    bundle.0.projection.scale = 0.5;
    commands.spawn(bundle);
}

fn follow(
    player: Query<&Transform, With<CameraTarget>>,
    mut camera: Query<&mut Transform, (With<BevyCamera>, Without<CameraTarget>)>,
) {
    if let Ok(player) = player.get_single() {
        camera.single_mut().translation = player.translation
    }
}