# Technical Design Document for {{GAME_NAME}}

## 1. Introduction
- **Purpose:** This document outlines the technical architecture, components, and implementation details for the WeChat Mini Game, "{{GAME_NAME}}".
- **Target Audience:** Development team, QA team, and technical stakeholders.
- **Related Documents:** Game Design Document, MVP Plan.

## 2. System Architecture
- A high-level diagram illustrating the overall architecture.

```
+------------------------+      +-----------------------+      +----------------------+
|   WeChat Mini Game     |      |                       |      |                      |
|       (Client)         |----->|   Game Backend Server   |----->|      Database        |
|                        |      |    (e.g., Node.js)    |      | (e.g., MongoDB, MySQL) |
| - Game Logic (JS/TS)   |<-----|                       |<-----|                      |
| - Rendering (Canvas)   |      +-----------------------+      +----------------------+
| - WeChat APIs          |
+------------------------+
           ^
           |
+------------------------+
| WeChat Open Data       |
| Context (for Social)   |
+------------------------+
```

## 3. Client-Side Architecture (WeChat Mini Game)
- **Programming Language:** JavaScript / TypeScript (Specify which one and the version).
- **Engine/Framework:** Native WeChat Mini Game framework.
- **Directory Structure:**
  ```
  / (root)
  |-- /assets
  |   |-- /images
  |   |-- /audio
  |-- /js
  |   |-- /libs (third-party libraries)
  |   |-- /main.js (entry point)
  |   |-- /game-logic.js
  |   |-- /ui-components.js
  |-- /pages
  |   |-- /index
  |   |-- /game
  |-- app.js
  |-- app.json
  |-- app.wxss
  |-- project.config.json
  ```
- **State Management:** How will the application state be managed? (e.g., Global object, simple event bus, a lightweight state management library).
- **Key Components / Modules:**
  - **`GameManager`:** Controls the main game loop, state transitions (e.g., main menu, playing, game over).
  - **`InputHandler`:** Manages user input (touch events).
  - **`AssetLoader`:** Handles loading of images, audio, and other assets.
  - **`Renderer`:** Responsible for drawing all game objects to the canvas.
  - **`APIWrapper`:** A module to wrap all `wx.` API calls for easier management and mocking.

## 4. Backend Architecture (if applicable)
- **Platform:** (e.g., Node.js with Express, Serverless Framework on Tencent Cloud).
- **Database Schema:**
  - **`Users` Collection/Table:**
    - `_id`: (Primary Key)
    - `openId`: (WeChat User ID)
    - `nickname`: String
    - `avatarUrl`: String
    - `highScore`: Number
    - `lastLogin`: Date
  - **Other Collections/Tables...**
- **API Endpoints:**
  - `POST /api/login`: Authenticates the user with a code from `wx.login` and returns a session token.
  - `GET /api/user/:id`: Retrieves user profile data.
  - `POST /api/score`: Submits a new score for the user.
  - `GET /api/leaderboard`: Retrieves the global or friend leaderboard.

## 5. Data Persistence
- **Client-Side:**
  - **`wx.setStorageSync` / `wx.getStorageSync`:** Used for storing non-critical data like user settings (e.g., sound on/off).
  - **`wx.setStorage` / `wx.getStorage`:** Used for asynchronous storage of data like the local high score.
- **Server-Side:**
  - The primary database will be the source of truth for all critical user data.

## 6. WeChat API Integration
- **`wx.login`:** For user authentication.
- **`wx.getUserProfile`:** To get user's nickname and avatar.
- **Open Data Context & `wx.getFriendCloudStorage`:** For implementing friend leaderboards without needing a custom backend.
- **`wx.shareAppMessage`:** For sharing functionality.
- **`wx.createInnerAudioContext`:** For sound effects and music.
- **`wx.request`:** For all communication with the backend server.

## 7. Performance Considerations
- **Asset Optimization:** All images will be compressed (e.g., using TinyPNG) and sized appropriately. Audio files will be in a compressed format (e.g., MP3).
- **Draw Call Batching:** Where possible, similar sprites will be drawn together to reduce draw calls.
- **Object Pooling:** Re-use objects (like enemies or projectiles) instead of creating and destroying them frequently to reduce garbage collection overhead.
- **Code Subpackaging:** For larger games, use WeChat's subpackaging feature to reduce the initial download size.

## 8. Error Handling & Logging
- **Client-Side:** `try...catch` blocks for critical operations. A global error handler to catch unhandled exceptions.
- **Logging:** Use a remote logging service (or a simple backend endpoint) to log critical errors for easier debugging of issues in the wild.

## 9. Security
- **Authentication:** The backend will securely exchange the `js_code` from `wx.login` for a `session_key` and `openid` from WeChat's servers. This `session_key` will be used to verify the integrity of subsequent requests.
- **Data Transfer:** All communication between the client and server will be over HTTPS.