bevy-game-engine

# Bevy Game Engine Expert knowledge for developing games with Bevy, the data-driven game engine built in Rust with a focus on ergonomics, modularity, and performance. ## When to Use This Skill | Use this skill when... | Use bevy-ecs-patterns instead when... | |------------------------|---------------------------------------| | Starting a new Bevy game project | Optimizing ECS query performance or archetype layout | | Learning or applying basic ECS concepts | Implementing complex system scheduling or ordering | | Handling input (keyboard, mouse, gamepad) | Using change detection (`Changed<T>`, `Added<T>`) | | Managing game states and transitions | Working with `ParamSet` or parallel query iteration | | Loading and managing assets | Designing entity relationship hierarchies | | Setting up plugins and app structure | Debugging archetype fragmentation or storage strategies | | Working with events and resources | Implementing batch spawn or deferred operations | ## Core Expertise **Bevy Architecture** - **Entity Component System (ECS)**: Data-oriented design with entities, components, and systems - **Plugin System**: Modular game organization with reusable plugins - **Schedules**: System ordering and execution timing - **Resources**: Global singleton data accessible to systems - **Events**: Typed message passing between systems - **States**: Game state management and transitions **Rendering** - **2D Rendering**: Sprites, sprite sheets, text rendering, 2D cameras - **3D Rendering**: PBR materials, meshes, lighting, shadows, cameras - **UI**: bevy_ui for in-game interfaces - **Shaders**: Custom WGSL shaders and render pipelines ## Reference Files The ECS core, project setup, and the command set below are everything a first pass needs. Follow one link when the task calls for it — nothing under `references/` is loaded unless you open it. | Path you are on | File | Carries | |---|---|---| | Reading player input | [`references/input.md`](references/input.md) | `ButtonInput` keyboard/mouse polling, pressed vs just-pressed, cursor position, gamepad and rebinding pointers | | Loading assets, or driving the state machine | [`references/assets-and-states.md`](references/assets-and-states.md) | `AssetServer` handles and `LoadState` gating, `States` enum, `OnEnter`/`OnExit`/`run_if(in_state)`, `NextState` timing | | Decoupling two systems that must communicate | [`references/events.md`](references/events.md) | `#[derive(Event)]`, `EventWriter`/`EventReader`, `add_event` registration, the two-frame buffer and ordering caveat | | Laying out a growing game, or chasing frame time | [`references/project-architecture.md`](references/project-architecture.md) | Directory layout, plugin/marker-component organization, query-filter and profiling guidance, bundles and system sets | ## Key Capabilities **ECS Fundamentals** ```rust use bevy::prelude::*; // Components are plain data structs #[derive(Component)] struct Player; #[derive(Component)] struct Health(f32); #[derive(Component)] struct Velocity(Vec2); // Spawn entities with components fn spawn_player(mut commands: Commands) { commands.spawn(( Player, Health(100.0), Velocity(Vec2::ZERO), SpriteBundle { transform: Transform::from_xyz(0.0, 0.0, 0.0), ..default() }, )); } // Systems query for components fn move_player( time: Res<Time>, mut query: Query<(&Velocity, &mut Transform), With<Player>>, ) { for (velocity, mut transform) in &mut query { transform.translation += velocity.0.extend(0.0) * time.delta_seconds(); } } ``` **App Structure** ```rust use bevy::prelude::*; fn main() { App::new() // Default plugins (window, rendering, input, etc.) .add_plugins(DefaultPlugins) // Custom plugins .add_plugins(GamePlugin) // Resources .insert_resource(GameSettings::default()) // Startup systems (run once) .add_systems(Startup, setup) // Update systems (run every frame) .add_systems(Update, ( player_movement, collision_detection, update_score, )) .run(); } // Organize with plugins pub struct GamePlugin; impl Plugin for GamePlugin { fn build(&self, app: &mut App) { app.add_systems(Startup, spawn_player) .add_systems(Update, player_input); } } ``` ## Essential Commands ```bash # Create new Bevy project from the official template (recommended — ships an # opinionated app skeleton, CI, and release profiles). See rust-plugin's # cargo-generate skill. cargo generate --git https://github.com/TheBevyFlock/bevy_new_2d --name my_game # Or start from an empty crate cargo new my_game cd my_game cargo add bevy # Run with fast compile times (debug) cargo run # Run with optimizations cargo run --release # Enable dynamic linking for faster compiles (dev only) cargo run --features bevy/dynamic_linking # Common dev dependencies cargo add bevy_egui # Debug UI cargo add bevy_rapier2d # 2D physics cargo add bevy_rapier3d # 3D physics cargo add bevy_asset_loader # Asset loading helpers cargo add leafwing-input-manager # Advanced input ``` ## Agentic Optimizations | Context | Command | |---------|---------| | Quick compile check | `cargo check 2>&1 \| head -30` | | Fast test run | `cargo test --lib -- --test-threads=1 -q` | | Run with fast compiles (dev) | `cargo run --features bevy/dynamic_linking` | | Run optimized build | `cargo run --release` | | Check for common issues | `cargo clippy -- -W clippy::all 2>&1 \| head -50` | | List plugins in project | `grep -rn "impl Plugin for" src/ --include="*.rs"` | | List game states | `grep -rn "derive.*States" src/ --include="*.rs"` | | Find event definitions | `grep -rn "derive.*Event" src/ --include="*.rs"` | | List dependencies | `cargo metadata --format-version=1 \| jq -r '.packages[0].dependencies[].name'` | For detailed ECS patterns, advanced queries, and system scheduling, see the bevy-ecs-patterns skill.