bevy-playground/src/camera.rs

use bevy::prelude::*;

use crate::player::Player;
use bevy::render::camera::Camera as BevyCamera;

pub struct Camera;

impl Plugin for Camera {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, spawn)
            .add_systems(PostUpdate, focus)
            .add_systems(Update, y_sort);
    }
}

fn spawn(mut commands: Commands) {
    let mut bundle = Camera2dBundle::default();
    bundle.projection.scale = 1. / 2.;
    commands.spawn(bundle);
}

fn focus(
    player: Query<&Transform, With<Player>>,
    mut camera: Query<&mut Transform, (With<BevyCamera>, Without<Player>)>,
) {
    camera.single_mut().translation = player.single().translation
}

fn y_sort(mut q: Query<&mut Transform>) {
    q.for_each_mut(|mut tf| tf.translation.z = -tf.translation.y)
}