bevy-playground/src/camera.rs

use bevy::prelude::*;

use crate::player;

pub struct Camera;

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

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::Player>>,
    mut camera: Query<
        &mut Transform,
        (With<bevy::render::camera::Camera>, Without<player::Player>),
    >,
) {
    let ply = player.single();
    let mut camt = camera.single_mut();
    camt.translation = ply.translation
}