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+# Enum Type Definitions
+
+This document defines the enumeration types used throughout the TeyvatGuide project, following the project's standard definition pattern.
+
+## Directory Structure
+
+Types can be defined in `src/types/` or at project root `types/`. Enum constants go in `enum/`. See [SKILL.md](./SKILL.md) for the complete project structure.
+
+## Definition Steps
+
+### Step 1: Define Type
+
+In `src/types/<Module>/<Module>.d.ts` or `types/<Module>.d.ts`, define a `const` object and its corresponding type:
+
+```typescript
+// src/types/BBS/Post.d.ts (or types/BBS/Post.d.ts)
+declare namespace TGApp.BBS.Post {
+  /**
+   * News type
+   * @since Beta v0.9.1
+   */
+  const NewsType = <const>{
+    /** Notice */
+    NOTICE: 1,
+    /** Activity */
+    ACTIVITY: 2,
+    /** News */
+    NEWS: 3,
+  };
+
+  /**
+   * News type enum
+   * @since Beta v0.9.1
+   */
+  type NewsTypeEnum = (typeof NewsType)[keyof typeof NewsType];
+}
+```
+
+### Step 2: Define Enum Constant
+
+In `src/enum/<Module>.ts`, define the corresponding enum constant:
+
+```typescript
+// src/enum/bbs.ts
+import TGApp from "../types/BBS/Post.d.ts";
+
+/**
+ * News type
+ * @since Beta v0.9.1
+ * @see TGApp.BBS.Post.NewsType
+ */
+const PostNewsTypeEnum: typeof TGApp.BBS.Post.NewsType = {
+  NOTICE: 1,
+  ACTIVITY: 2,
+  NEWS: 3,
+};
+```
+
+## Naming Conventions
+
+| Type | Naming Rule | Example |
+|------|-------------|---------|
+| const object | `<Feature>Type` | `NewsType`, `PostViewType` |
+| type alias | `<Feature>TypeEnum` | `NewsTypeEnum`, `ViewTypeEnum` |
+| enum constant | `<Feature>TypeEnum` | `PostNewsTypeEnum`, `AvatarExtTypeEnum` |
+| readonly list | `<Feature>TypeList` | `PostNewsTypeList` |
+| description function | `get<Type>Desc` | `getPostNewsTypeDesc` |
+
+## Complete Example
+
+### 1. Define Type (Post.d.ts)
+
+```typescript
+declare namespace TGApp.BBS.Post {
+  /**
+   * View type
+   * @since Beta v0.8.4
+   */
+  const PostViewType = <const>{
+    /** Normal post */
+    NORMAL: 1,
+    /** Image post, such as fan art, COS */
+    PIC: 2,
+    /** Video post */
+    VOD: 5,
+    /** UGC Thousand Stars Realm */
+    UGC: 7,
+  };
+
+  /**
+   * View type enum
+   * @since Beta v0.8.4
+   */
+  type ViewTypeEnum = (typeof PostViewType)[keyof typeof PostViewType];
+}
+```
+
+### 2. Define Enum Constant (bbs.ts)
+
+```typescript
+/**
+ * Post view type
+ * @since Beta v0.8.4
+ * @see TGApp.BBS.Post.ViewTypeEnum
+ */
+const PostViewTypeEnum: typeof TGApp.BBS.Post.PostViewType = {
+  NORMAL: 1,
+  PIC: 2,
+  VOD: 5,
+  UGC: 7,
+};
+```
+
+### 3. Export Aggregated Object (bbs.ts)
+
+```typescript
+/** MiHoYo BBS related enums */
+const bbsEnum = {
+  /** Post related enums */
+  post: {
+    viewType: PostViewTypeEnum,
+    // ...
+  },
+};
+
+export default bbsEnum;
+```
+
+## Key Rules
+
+1. **Use `<const>` assertion**: Ensures the type is readonly
+2. **Type derivation**: Use `(typeof Type)[keyof typeof Type]` pattern to derive union types
+3. **JSDoc comments**: Every enum needs `@since` and `@see` comments
+4. **Naming consistency**: Enum constant names in .ts files should match const object names in .d.ts files
+5. **Export aggregated objects**: Group related enums in a default export object