stories/src/main.rs

use bevy::prelude::*;

#[derive(Component)]
struct Mover;

fn main() {
    App::new()
        .insert_resource(Movement { dx: 0.0, dy: 0.0 })
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, (input, decay, movement))
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(0.0, 12.0, 18.0).looking_at(Vec3::ZERO, Vec3::Y),
            ..default()
        },
        Mover,
    ));

    commands.spawn(PointLightBundle {
        point_light: PointLight {
            shadows_enabled: true,
            ..default()
        },
        transform: Transform::from_xyz(4.0, 8.0, 4.0),
        ..default()
    });

    for x in 0..24 {
        for y in 0..24 {
            let x = x - 12;
            let y = y - 12;
            let z = if x == -12 || x == 11 || y == -12 || y == 11 || rand::random::<f32>() < 0.25 {
                0.0
            } else {
                -2.0
            };
            let rotation = match rand::random::<u8>() % 4 {
                0 => 0.0,
                1 => 0.5,
                2 => 1.0,
                _ => 1.5,
            } * std::f32::consts::PI;
            commands.spawn(SceneBundle {
                scene: asset_server.load("test-cube.glb#Scene0"),
                transform: Transform::from_xyz((x * 2) as f32, z, (y * 2) as f32)
                    .with_rotation(Quat::from_rotation_y(rotation)),
                ..default()
            });
        }
    }
}

#[derive(Debug, Resource)]
struct Movement {
    dx: f32,
    dy: f32,
}

impl Default for Movement {
    fn default() -> Movement {
        Movement { dx: 0.0, dy: 0.0 }
    }
}

const ACCEL: f32 = 0.002;

fn input(keyboard: Res<ButtonInput<KeyCode>>, mut mvmt: ResMut<Movement>) {
    if keyboard.pressed(KeyCode::ArrowUp) {
        mvmt.dy = (mvmt.dy - ACCEL).clamp(-0.5, 0.5);
    }
    if keyboard.pressed(KeyCode::ArrowDown) {
        mvmt.dy = (mvmt.dy + ACCEL).clamp(-0.5, 0.5);
    }
    if keyboard.pressed(KeyCode::ArrowLeft) {
        mvmt.dx = (mvmt.dx - ACCEL).clamp(-0.5, 0.5);
    }
    if keyboard.pressed(KeyCode::ArrowRight) {
        mvmt.dx = (mvmt.dx + ACCEL).clamp(-0.5, 0.5);
    }
}

fn decay(mut mvmt: ResMut<Movement>) {
    if mvmt.dx.abs() < 0.001 {
        mvmt.dx = 0.0;
    } else {
        mvmt.dx *= 0.90;
    }

    if mvmt.dy.abs() < 0.001 {
        mvmt.dy = 0.0;
    } else {
        mvmt.dy *= 0.90;
    }
}

fn movement(mut query: Query<&mut Transform, With<Mover>>, mvmt: Res<Movement>, time: Res<Time>) {
    if time.delta_seconds() == 0.0 {
        return;
    }

    for mut transform in &mut query {
        transform.translation += Vec3::new(
            mvmt.dx / time.delta_seconds(),
            0.0,
            mvmt.dy / time.delta_seconds(),
        );
    }
}