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Bevy ECS Expert

Master Bevy's Entity Component System (ECS) in Rust, covering Systems, Queries, Resources, and parallel scheduling.

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Install this skill Read the source first Free Written by sickn33 · unverified publisher
Context cost
925 tokensestimated from the bundle, loaded when it triggers
Bundle
1 file · 3.7 kBtext throughout, nothing executable
Licence
MITfree to use
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Master Bevy's Entity Component System (ECS) in Rust, covering Systems, Queries, Resources, and parallel scheduling.

Installed, it changes the agent in these ways.

What this skill changes about the agent is not written down here yet. The listing was collected from its source, and the description is in its own SKILL.md.

Expertise

Domain judgement the base model does not have.

gamedevrust
Filed under

Developer Tools & Repos

The skill itself

This is the whole product. A skill is instructions the model reads, so there is nothing behind the listing you cannot see first — the front matter loads with every session, and the body below it loads when the skill triggers.

SKILL.md3.7 kB · 142 lines
--- name: bevy-ecs-expert description: "Master Bevy's Entity Component System (ECS) in Rust, covering Systems, Queries, Resources, and parallel scheduling." risk: safe source: community date_added: "2026-02-27" ---
9# Bevy ECS Expert
10
11## Overview
12
13A guide to building high-performance game logic using Bevy's data-oriented ECS architecture. Learn how to structure systems, optimize queries, manage resources, and leverage parallel execution.
14
15## When to Use This Skill
16
17- Use when developing games with the Bevy engine in Rust.
18- Use when designing game systems that need to run in parallel.
19- Use when optimizing game performance by minimizing cache misses.
20- Use when refactoring object-oriented logic into data-oriented ECS patterns.
21
22## Step-by-Step Guide
23
24### 1. Defining Components
25
26Use simple structs for data. Derive Component and Reflect.
27
28```rust
29#[derive(Component, Reflect, Default)]
30#[reflect(Component)]
31struct Velocity {
32 x: f32,
33 y: f32,
34}
35
36#[derive(Component)]
37struct Player;
38```
39
40### 2. Writing Systems
41
42Systems are regular Rust functions that query components.
43
44```rust
45fn movement_system(
46 time: Res<Time>,
47 mut query: Query<(&mut Transform, &Velocity), With<Player>>,
48) {
49 for (mut transform, velocity) in &mut query {
50 transform.translation.x += velocity.x * time.delta_seconds();
51 transform.translation.y += velocity.y * time.delta_seconds();
52 }
53}
54```
55
56### 3. Managing Resources
57
58Use Resource for global data (score, game state).
59
60```rust
61#[derive(Resource)]
62struct GameState {
63 score: u32,
64}
65
66fn score_system(mut game_state: ResMut<GameState>) {
67 game_state.score += 10;
68}
69```
70
71### 4. Scheduling Systems
72
73Add systems to the App builder, defining execution order if needed.
74
75```rust
76fn main() {
77 App::new()
78 .add_plugins(DefaultPlugins)
79 .init_resource::<GameState>()
80 .add_systems(Update, (movement_system, score_system).chain())
81 .run();
82}
83```
84
85## Examples
86
87### Example 1: Spawning Entities with Require Component
88
89```rust
90use bevy::prelude::*;
91
92#[derive(Component, Reflect, Default)]
93#[require(Velocity, Sprite)]
94struct Player;
95
96#[derive(Component, Default)]
97struct Velocity {
98 x: f32,
99 y: f32,
100}
101
102fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
103 commands.spawn((
104 Player,
105 Velocity { x: 10.0, y: 0.0 },
106 Sprite::from_image(asset_server.load("player.png")),
107 ));
108}
109```
110
111### Example 2: Query Filters
112
113Use With and Without to filter entities efficiently.
114
115```rust
116fn enemy_behavior(
117 query: Query<&Transform, (With<Enemy>, Without<Dead>)>,
118) {
119 for transform in &query {
120 // Only active enemies processed here
121 }
122}
123```
124
125## Best Practices
126
127- ✅ **Do:** Use Query filters (With, Without, Changed) to reduce iteration count.
128- ✅ **Do:** Prefer Res over ResMut when read-only access is sufficient to allow parallel execution.
129- ✅ **Do:** Use Bundle to spawn complex entities atomically.
130- ❌ **Don't:** Store heavy logic inside Components; keep them as pure data.
131- ❌ **Don't:** Use RefCell or interior mutability inside components; let the ECS handle borrowing.
132
133## Troubleshooting
134
135**Problem:** System panic with "Conflict" error.
136**Solution:** You are likely trying to access the same component mutably in two systems running in parallel. Use .chain() to order them or split the logic.
137
138## Limitations
139- Use this skill only when the task clearly matches the scope described above.
140- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
141- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.
142
In the file
SKILL.md482 words
Files1
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈50
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
875
on trigger
The instruction body, read only when the skill fires.
0.46%
of a 200k window
Ten skills this size would take about 5% of the window before you open a file.
050k100k150k200k context window

925 tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Small enough to keep loaded permanently without thinking about it.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

Adoption
Installsnone yet
Ratingno reviews yet

The procedure it runs

The procedure has not been published here. It is in the skill’s own SKILL.md, which its author has not sent to the marketplace yet.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

It writes no files and reaches no network. All it changes is how the model reasons and writes.

What it asks for
Writes filesno
Network accessno

Read from the allowed-tools line of this skill’s own SKILL.md. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

1 file, 3.7 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md3.7 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Bevy ECS Expert · 925 tokens when loaded npx mcprush@latest skill add sickn33/bevy-ecs-expert

Writes to .claude/skills/bevy-ecs-expert/ in the current project. Add --global to put it in your home directory instead, for every project.

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This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencesickn33/bevy-ecs-expert

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v
  • No earlier releases have been published to the marketplace.
Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

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Who wrote it

SI
sickn33

Publishes on mcprush.

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