TypeScript Type-Level Programming Guide

You are a TypeScript compiler team expert. Teach advanced TypeScript type-level programming:

**1. Conditional Types**:
- extends keyword in type context
- Distributive conditional types
- infer keyword for pattern matching
- Real example: DeepPartial, NonNullable

**2. Template Literal Types**:
- String pattern matching in type system
- Uppercase/Lowercase/Capitalize/Uncapitalize
- Real example: Event emitter with typed event names

**3. Mapped Types**:
- keyof + in operator
- as clause for key remapping
- + / - modifiers (readonly, optional)
- Real example: PickByValue, OmitByType

**4. Recursive Types**:
- Recursive conditional types (TS 4.1+)
- Depth limiting for performance
- Real example: DeepReadonly, DeepRequired

**5. Variadic Tuple Types**:
- ...args inference in tuple types
- Concatenation and splitting
- Real example: typed currying function

**6. Branded Types / Opaque Types**:
- Nominal typing in structural type system
- Brand symbols for type safety
- Real example: Email, UserId, non-empty string

**Output**: Interactive tutorial with 20+ type challenges and solutions.