So I want to update the sprite so my character looks in a different direction each time the player presses left/right, how could I do this? I can't do it in the setup fn, since it's a startup system, appreciate any help

EDIT: changed formating

here is my code:

use bevy::prelude::*;

`fn main() {
    App::new()
        .add_plugins(DefaultPlugins.set(ImagePlugin::default_nearest())) // prevents blurry sprites
        .add_systems(Startup, setup)
        .add_systems(Update, animate_sprite)
        .add_systems(Update, player_movement_system)
        .run();
}

const BOUNDS: Vec2 = Vec2::new(1200.0, 640.0);
static mut FLIP_BOOLEAN: bool = false;

fn set_flip_boolean(boolean: bool) {
    unsafe {
        FLIP_BOOLEAN = boolean;
    }
}

fn get_flip_boolean() -> bool{
    unsafe {
        FLIP_BOOLEAN
    }
}

#[derive(Component)]
struct Player {
    movement_speed: f32,
}

#[derive(Component)]
struct AnimationIndices {
    first: usize,
    last: usize,
}

#[derive(Component, Deref, DerefMut)]
struct AnimationTimer(Timer);

fn animate_sprite(
    time: Res<Time>,
    mut query: Query<(&AnimationIndices, &mut AnimationTimer, &mut TextureAtlas)>,
) {
    for (indices, mut timer, mut atlas) in &mut query {
        timer.tick(time.delta());
        if timer.just_finished() {
            atlas.index = if atlas.index == indices.last {
                indices.first
            } else {
                atlas.index + 1
            };
        }
    }
}


fn setup(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut texture_atlas_layouts: ResMut<Assets<TextureAtlasLayout>>,
) {
    let texture = asset_server.load("sprites/Idle01.png");
    let layout = TextureAtlasLayout::from_grid(Vec2::new(64.0, 40.0), 5, 1, None, None);
    let texture_atlas_layout = texture_atlas_layouts.add(layout);
    let animation_indices = AnimationIndices { first: 0, last: 4 };
    let boolean = get_flip_boolean();
    commands.spawn(Camera2dBundle::default());
    commands.spawn((
        SpriteSheetBundle {
            texture,
            atlas: TextureAtlas {
                layout: texture_atlas_layout,
                index: animation_indices.first,
            },
            
            ..default()
        },
        Player {
            movement_speed: 500.0,
        },
        animation_indices,
        AnimationTimer(Timer::from_seconds(0.1, TimerMode::Repeating)),
    ));
}

fn player_movement_system(
    time: Res<Time>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
    mut query: Query<(&Player, &mut Transform)>,
) {
    let (guy, mut transform) = query.single_mut();

    let mut movement_factor = 0.0;

    let mut movement_direction = Vec3::X;

    if keyboard_input.pressed(KeyCode::ArrowLeft) {
        movement_factor -= 1.0;
        movement_direction = Vec3::X;
        set_flip_boolean(true);
    }

    if keyboard_input.pressed(KeyCode::ArrowRight) {
        movement_factor += 1.0;
        movement_direction = Vec3::X;
        set_flip_boolean(false);
    }

    if keyboard_input.pressed(KeyCode::ArrowUp) {
        movement_factor += 1.0;
        movement_direction = Vec3::Y;
    }

    if keyboard_input.pressed(KeyCode::ArrowDown) {
        movement_factor -= 1.0;
        movement_direction = Vec3::Y;
    }


    let movement_distance = movement_factor * guy.movement_speed * time.delta_seconds();
    let translation_delta = movement_direction * movement_distance;
    transform.translation += translation_delta;

    let extents = Vec3::from((BOUNDS / 2.0, 0.0));
    transform.translation = transform.translation.min(extents).max(-extents);
}

Been working on this a few months. It's inspired by previous generations of parser generators, and by my own previous work generating ast lexers from grammar files. This integrates seamlessly with the type system, allowing you to declare your syntax, extract only the data you want as variables, and evaluate them easily. And just from a simple description of your syntax, you'll get beautiful errors which visually point out structures in the input.

With this I have been able to implement a (mostly complete) JSON parser in just 12 lines of parsing logic, and a pmdas-respecting expression parser in just 6 (with one helper function to apply individual operators).

Examples available on the github repo, also now available on crates.io!

I recently made a fairly simple shader heavily inspired by the one used for characters in The Legend of Zelda: The Wind Waker. I've got all my info on how it worked on the GameCube from this amazing video

Check out the source at bevy_wind_waker_shader

Here are some screenshots :)

Sphere:

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Light throughout day:

Daylight

​

Night time