# Unity ECS Patterns

Production patterns for Unity's Data-Oriented Technology Stack (DOTS) including Entity Component System, Job System, and Burst Compiler.

## When to Use This Skill

- Building high-performance Unity games
- Managing thousands of entities efficiently
- Implementing data-oriented game systems
- Optimizing CPU-bound game logic
- Converting OOP game code to ECS
- Using Jobs and Burst for parallelization

## Core Concepts

### 1. ECS vs OOP

| Aspect      | Traditional OOP   | ECS/DOTS        |
| ----------- | ----------------- | --------------- |
| Data layout | Object-oriented   | Data-oriented   |
| Memory      | Scattered         | Contiguous      |
| Processing  | Per-object        | Batched         |
| Scaling     | Poor with count   | Linear scaling  |
| Best for    | Complex behaviors | Mass simulation |

### 2. DOTS Components

```
Entity: Lightweight ID (no data)
Component: Pure data (no behavior)
System: Logic that processes components
World: Container for entities
Archetype: Unique combination of components
Chunk: Memory block for same-archetype entities
```

## Detailed patterns and worked examples

Detailed pattern documentation lives in `references/details.md`. Read that file when the navigation tier above is insufficient.

## Best Practices

### Do's

- **Use ISystem over SystemBase** - Better performance
- **Burst compile everything** - Massive speedup
- **Batch structural changes** - Use ECB
- **Profile with Profiler** - Identify bottlenecks
- **Use Aspects** - Clean component grouping

### Don'ts

- **Don't use managed types** - Breaks Burst
- **Don't structural change in jobs** - Use ECB
- **Don't over-architect** - Start simple
- **Don't ignore chunk utilization** - Group similar entities

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