bevy-playground/src/movement.rs

use bevy::prelude::*;

#[derive(Component, Deref, DerefMut, Debug, Default)]
pub struct Velocity(pub Vec2);

#[derive(Component, Deref, DerefMut, Debug, Default)]
pub struct Heading(pub Vec2);

#[derive(Component, Deref, DerefMut, Debug, Default)]
pub struct Speed(pub f32);

#[derive(Component, Deref, DerefMut, Debug, Default)]
pub struct Height(pub f32);

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

pub fn resolve_velocity(mut query: Query<(&Velocity, &mut Transform)>, time: Res<Time>) {
    for (velocity, mut transform) in query.iter_mut() {
        transform.translation += (velocity.0 * time.delta_seconds()).extend(0.);
    }
}

pub fn update_velocity_by_heading(mut query: Query<(&mut Velocity, &Speed, &Heading)>) {
    if let Ok((mut velocity, speed, heading)) = query.get_single_mut() {
        **velocity = heading.normalize_or_zero() * (**speed);
    }
}

pub fn ysort(mut q: Query<(&mut Transform, Option<&Height>), With<YSortable>>) {
    q.iter_mut()
        .for_each(|(mut tf, z)| tf.translation.z = -tf.translation.y - z.map(|z| z.0).unwrap_or(0.))
}

#[derive(Bundle, Debug, Default)]
pub struct Mover {
    pub velocity: Velocity,
    pub heading: Heading,
    pub speed: Speed,
}