flappy bevy example

Cargo.toml

@@ -432,6 +432,10 @@ path = "examples/games/breakout.rs"
 name = "contributors"
 path = "examples/games/contributors.rs"
 
+[[example]]
+name = "flappy_bevy"
+path = "examples/games/flappy_bevy.rs"
+
 [[example]]
 name = "game_menu"
 path = "examples/games/game_menu.rs"

examples/README.md

@@ -205,6 +205,7 @@ Example | File | Description
 `alien_cake_addict` | [`games/alien_cake_addict.rs`](./games/alien_cake_addict.rs) | Eat the cakes. Eat them all. An example 3D game
 `breakout` | [`games/breakout.rs`](./games/breakout.rs) | An implementation of the classic game "Breakout"
 `contributors` | [`games/contributors.rs`](./games/contributors.rs) | Displays each contributor as a bouncy bevy-ball!
+`flappy_bevy` | [`games/flappy_bevy.rs`](./games/flappy_bevy.rs) | A flappy bird clone but with many birds
 `game_menu` | [`games/game_menu.rs`](./games/game_menu.rs) | A simple game menu
 
 ## Input

examples/games/flappy_bevy.rs

@@ -0,0 +1,282 @@
+//! A simplified Flappy Bird but with many birds. Press space to flap.
+
+use bevy::prelude::*;
+
+use bevy::sprite::collide_aabb::{collide, Collision};
+use bevy::window::PresentMode;
+
+use rand::random;
+
+const CHUNK_SIZE: f32 = 300.0;
+const CAMERA_SPEED: f32 = 120.0;
+const GAME_HEIGHT: f32 = 500.0;
+const SCREEN_HEIGHT: f32 = 1500.0;
+const CLEANUP_X_DIST: f32 = 1500.0;
+const BROWNIAN_DRIFT_AMOUNT_X: f32 = 250.0;
+const BROWNIAN_DRIFT_AMOUNT_Y: f32 = 600.0;
+const DRIFT_TO_CENTER_AMOUNT: f32 = 0.1;
+const FLAP_STRENGTH: f32 = 240.0;
+const BIRD_SIZE: f32 = 24.0;
+const BIRD_REPRODUCTION_CHANCE: f32 = 1.0;
+const MAX_BIRDS: usize = 500;
+const GRAVITY: f32 = 400.0;
+const GAP_VARIABILITY: f32 = 0.9;
+
+pub fn main() {
+    let mut app = App::new();
+
+    app.insert_resource(WindowDescriptor {
+        width: 1600.,
+        height: 900.,
+        title: "Flappy Bevy".to_string(),
+        present_mode: PresentMode::Immediate, // smooth but power hungry
+        resizable: true,
+        ..Default::default()
+    })
+    .add_plugins(DefaultPlugins)
+    .add_startup_system(spawn_camera)
+    .add_startup_system(load_art)
+    .add_startup_system(bird_startup)
+    .add_system(spawn_bird)
+    .add_system(bird_collision)
+    .add_system(bird_reproduction)
+    .add_system(bird_control.after(gravity))
+    .add_system(terrain_gen)
+    .add_system(advance_camera)
+    .add_system(brownian_drift)
+    .add_system(velocity)
+    .add_system(gravity)
+    .add_system(terrain_cleanup)
+    .add_system(drift_to_center)
+    .add_event::<GenerateChunk>()
+    .add_event::<SpawnBird>();
+
+    app.run();
+}
+
+pub struct Art {
+    bird_icon: Handle<Image>,
+}
+
+fn load_art(mut commands: Commands, asset_server: Res<AssetServer>) {
+    commands.insert_resource(Art {
+        bird_icon: asset_server.load("branding/icon.png"),
+    });
+}
+struct GenerateChunk {
+    new_chunk_index: i32,
+}
+
+fn advance_camera(
+    mut q: Query<&mut Transform, With<Camera>>,
+    time: Res<Time>,
+    mut outgoing_generate_chunk_events: EventWriter<GenerateChunk>,
+) {
+    if let Ok(mut transform) = q.get_single_mut() {
+        let chunk_index = (transform.translation.x / CHUNK_SIZE).floor() as i32;
+        transform.translation.x += time.delta().as_secs_f32() * CAMERA_SPEED;
+        let new_chunk_index = (transform.translation.x / CHUNK_SIZE).floor() as i32;
+        // if the camera has moved over a chunk boundary
+        if chunk_index != new_chunk_index {
+            // generate a new chunk offscreen to the right
+            outgoing_generate_chunk_events.send(GenerateChunk {
+                new_chunk_index: new_chunk_index + 3,
+            });
+        }
+    }
+}
+
+#[derive(Component)]
+struct Obstacle;
+
+fn terrain_cleanup(
+    mut commands: Commands,
+    q: Query<(Entity, &Transform), With<Obstacle>>,
+    cam: Query<&Transform, With<Camera>>,
+) {
+    let cam_x = cam.single().translation.x;
+    for (e, t) in q.iter() {
+        // remove obstacles at the left
+        if t.translation.x < cam_x - CLEANUP_X_DIST {
+            commands.entity(e).despawn();
+        }
+    }
+}
+
+fn terrain_gen(
+    mut commands: Commands,
+    mut incoming_generate_chunk_events: EventReader<GenerateChunk>,
+) {
+    for ev in incoming_generate_chunk_events.iter() {
+        let x_pos = CHUNK_SIZE * ev.new_chunk_index as f32;
+        // generate some terrain within x_pos..x_pos+width
+        let gap_y_pos = GAME_HEIGHT * (random::<f32>() - 0.5) * GAP_VARIABILITY;
+        let pillar_width = 50.0 + 110.0 * random::<f32>();
+        // make the gap no narrower than the pillar is wide
+        let gap_size = (65.0 + 250.0 * random::<f32>()).max(pillar_width);
+        for (top_y_pos, bottom_y_pos) in [
+            (-SCREEN_HEIGHT * 0.5, gap_y_pos - gap_size * 0.5),
+            (gap_y_pos + gap_size * 0.5, SCREEN_HEIGHT * 0.5),
+        ] {
+            let pillar_origin = Vec2::new(x_pos, (top_y_pos + bottom_y_pos) * 0.5);
+            let pillar_size = Vec2::new(pillar_width, bottom_y_pos - top_y_pos);
+            commands
+                .spawn_bundle(SpriteBundle {
+                    sprite: Sprite {
+                        color: Color::rgb(0.25, 0.25, 0.75),
+                        custom_size: Some(pillar_size),
+                        ..default()
+                    },
+                    transform: Transform::from_translation(pillar_origin.extend(0.0)),
+                    ..default()
+                })
+                .insert(Obstacle);
+        }
+    }
+}
+
+fn spawn_camera(mut commands: Commands) {
+    commands.spawn_bundle(Camera2dBundle::default());
+}
+
+#[derive(Component, Default)]
+struct Velocity {
+    velocity: Vec2,
+}
+
+#[derive(Component)]
+struct BrownianDrift;
+
+#[derive(Component)]
+struct Gravity;
+
+#[derive(Component)]
+struct Bird;
+
+#[derive(Component)]
+struct DriftToCenter;
+
+/// Event that causes a new bird to spawn
+struct SpawnBird {
+    new_bird_pos: Vec2,
+    new_bird_velocity: Vec2,
+}
+
+fn bird_startup(mut spawn_bird_events: EventWriter<SpawnBird>) {
+    spawn_bird_events.send(SpawnBird {
+        new_bird_pos: Vec2::ZERO,
+        new_bird_velocity: Vec2::new(CAMERA_SPEED, 0.0),
+    });
+}
+
+fn spawn_bird(
+    mut commands: Commands,
+    mut spawn_bird_events: EventReader<SpawnBird>,
+    art: Res<Art>,
+) {
+    for ev in spawn_bird_events.iter() {
+        commands
+            .spawn_bundle(SpriteBundle {
+                sprite: Sprite {
+                    color: Color::rgb(random::<f32>(), random::<f32>(), random::<f32>()),
+                    custom_size: Some(Vec2::splat(BIRD_SIZE)),
+                    ..default()
+                },
+                texture: art.bird_icon.clone(),
+                transform: Transform::from_translation(
+                    ev.new_bird_pos.extend(random::<f32>() * 100.0),
+                ),
+                ..default()
+            })
+            .insert(Velocity {
+                velocity: ev.new_bird_velocity,
+            })
+            .insert(Gravity)
+            .insert(Bird)
+            .insert(BrownianDrift)
+            .insert(DriftToCenter);
+    }
+}
+
+/// The flock has a tendency to drift offscreen - gently bring it back to the center
+fn drift_to_center(
+    mut q: Query<(&mut Velocity, &Transform)>,
+    cam: Query<&Transform, With<Camera>>,
+    time: Res<Time>,
+) {
+    for (mut v, t) in q.iter_mut() {
+        v.velocity.x -= (t.translation.x - cam.single().translation.x)
+            * DRIFT_TO_CENTER_AMOUNT
+            * time.delta().as_secs_f32();
+    }
+}
+
+fn velocity(mut q: Query<(&Velocity, &mut Transform)>, time: Res<Time>) {
+    for (v, mut t) in q.iter_mut() {
+        t.translation += (v.velocity * time.delta().as_secs_f32()).extend(0.0);
+    }
+}
+
+fn gravity(mut q: Query<&mut Velocity, With<Gravity>>, time: Res<Time>) {
+    for mut v in q.iter_mut() {
+        v.velocity.y -= time.delta().as_secs_f32() * GRAVITY;
+    }
+}
+
+fn bird_collision(
+    mut commands: Commands,
+    birds: Query<(Entity, &Sprite, &Transform), With<Bird>>,
+    obstacles: Query<(&Sprite, &Transform), With<Obstacle>>,
+) {
+    for (bird_entity, bird_sprite, bird_transform) in birds.iter() {
+        let mut collision_result: Option<Collision> = None;
+        for (obstacle_sprite, obstacle_transform) in obstacles.iter() {
+            if collision_result.is_none() {
+                collision_result = collide(
+                    bird_transform.translation,
+                    bird_sprite.custom_size.unwrap(),
+                    obstacle_transform.translation,
+                    obstacle_sprite.custom_size.unwrap(),
+                );
+            }
+        }
+        if collision_result.is_some() || bird_transform.translation.y < -SCREEN_HEIGHT * 0.5 {
+            commands.entity(bird_entity).despawn();
+        }
+    }
+}
+
+fn bird_reproduction(
+    q: Query<(&Transform, &Velocity), With<Bird>>,
+    time: Res<Time>,
+    mut spawn_bird_events: EventWriter<SpawnBird>,
+) {
+    let bird_count = q.iter().count();
+    if bird_count < MAX_BIRDS {
+        for (t, v) in q.iter() {
+            if random::<f32>() < BIRD_REPRODUCTION_CHANCE * time.delta().as_secs_f32() {
+                spawn_bird_events.send(SpawnBird {
+                    new_bird_pos: t.translation.truncate(),
+                    new_bird_velocity: v.velocity,
+                });
+            }
+        }
+    }
+}
+
+fn brownian_drift(mut q: Query<&mut Velocity, With<BrownianDrift>>, time: Res<Time>) {
+    for mut v in q.iter_mut() {
+        v.velocity += Vec2::new(
+            (random::<f32>() - 0.5) * BROWNIAN_DRIFT_AMOUNT_X,
+            (random::<f32>() - 0.5) * BROWNIAN_DRIFT_AMOUNT_Y,
+        ) * time.delta().as_secs_f32();
+    }
+}
+
+fn bird_control(input: Res<Input<KeyCode>>, mut birds: Query<&mut Velocity, With<Bird>>) {
+    if input.just_pressed(KeyCode::Space) {
+        for mut v in birds.iter_mut() {
+            v.velocity.y = FLAP_STRENGTH;
+        }
+    }
+}