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DependencyInjection/README.md

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+# Simple Dependency Injection Container
+
+A learning project to understand how Dependency Injection works by building one from scratch.
+
+Inspired by the Phenix RTS platform's DI system.
+
+## Learning Goals
+
+1. Understand how DI containers resolve dependencies
+2. Learn about different lifecycle patterns (singleton, transient, factory)
+3. Understand circular dependency detection
+4. Learn about provider patterns
+5. Understand type registration and resolution
+
+## Steps
+
+We'll build this incrementally:
+
+1. **Step 1**: Basic container with manual registration
+2. **Step 2**: Constructor injection
+3. **Step 3**: Singleton vs Transient lifecycles
+4. **Step 4**: Circular dependency detection
+5. **Step 5**: Provider pattern
+6. **Step 6**: Named registrations
+7. **Step 7**: Configuration-driven DI (like Phenix's di.json)
+
+## Running the Examples
+
+```bash
+# Step 1 - Basic
+node step1-basic.js
+
+# Step 2 - Constructor Injection
+node step2-constructor-injection.js
+
+# Step 3 - Lifecycles
+node step3-lifecycles.js
+
+# Step 4 - Circular Dependencies
+node step4-circular-deps.js
+
+# Step 5 - Providers
+node step5-providers.js
+
+# Step 6 - Named Registrations
+node step6-named.js
+
+# Step 7 - Configuration
+node step7-config.js
+```
+
+## Key Concepts
+
+### Dependency Injection
+
+Instead of creating dependencies inside a class, they are "injected" from outside.
+
+### Inversion of Control (IoC)
+
+The container controls object creation and lifecycle, not your code.
+
+### Service Locator vs DI
+
+DI is better because dependencies are explicit in constructor signatures.
+
+## Architecture
+
+```
+Container
+├── Registry (stores type registrations)
+├── Resolver (resolves dependencies)
+├── Lifecycle Manager (handles singleton/transient)
+└── Provider System (custom creation logic)
+```