Add doc.

Author: jcs090218

README.md

@@ -4,6 +4,47 @@
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
 # Unity Lua
-> Use Lua scripting language in Unity to accomplish hot update/fox functionalitiy.
+> Use Lua scripting language in Unity to accomplish hot update/fix functionality.
 
 Project built on top of the [tolua](https://github.com/topameng/tolua) by [topameng](https://github.com/topameng).
+
+This is the minimal project that shows you how to use `tolua` in your
+own project.
+
+## Why use ToLua for your game?
+
+When you came of hot-update, you would need a scripting language that can be
+compile or use after the binary is built.
+
+### Pros
+
+* Hot update/fix - you are able to change game logic without compile from
+C# to binary.
+* Lua is easy to learn.
+
+### Cons
+
+* No auto-completion and debugging tool. (Maybe in the future?)
+* You would have to do extra comilation every time you want to port a function
+from C# to Lua programming interface.
+
+## About ToLua
+
+Here is a quick start that teaches you to use `tolua` in under a minute.
+
+* `Assets/ToLua/Editor/Custom/CustomSettings.cs`
+* `Assets/ToLua/Source/LuaConst.cs`
+
+These files are the only files that you need to be aware of to customize `tolua`.
+Basically all the export and path settings are listed in these files.
+
+Done!!!
+
+## Examples
+
+There are few files that you would need to see before you know how to use 
+`tolua`'s functionality.
+
+All C# & Lua scripts under `/Assets/_Project/Scripts` folder.
+
+Done!!!