update README.md

README.md

@@ -1,19 +1,49 @@
 # 2048-api
 A 2048 game api for training supervised learning (imitation learning) or reinforcement learning agents
 
-# To compile the pre-defined [ExpectiMax](https://github.com/nneonneo/2048-ai) agent
+# Code structure
+* [`game2048/`](game2048/): the main package.
+    * [`game.py`](game2048/game.py): the core 2048 `Game` class.
+    * [`agents.py`](game2048/agents.py): the `Agent` class with instances.
+    * [`displays`](game2048/displays.py): the `Display` class with instances, to show the `Game` state.
+    * [`expectimax/`](game2048/expectimax): a powerful ExpectiMax agent by [here](https://github.com/nneonneo/2048-ai).
+* [`explore.ipynb`](explore.ipynb): introduce how to use the `Agent`, `Display` and `Game`.
+* [`static/`](static/): html assets for web app.
+* [`webapp.py`](webapp.py): run the web app demo.
+* [`evaluate.py`](evaluate.py): evaluate your self-defined agent.
+
+# To define your own agents
+```python
+from game2048.agents import Agent
+
+class YourOwnAgent(Agent):
+
+    def step(self):
+        '''To define the agent's 1-step behavior given the `game`.
+        You can find more instance in [`agents.py`](game2048/agents.py).
+        
+        :return direction: 0: left, 1: down, 2: right, 3: up
+        '''
+        direction = some_function(self.game)
+        return direction
+
+```
+
+# To compile the pre-defined ExpectiMax agent
 
 ```bash
 cd game2048/expectimax
 bash configure
 make
 ```
 
-# To run the webapp
+# To run the web app
 ```bash
 python webapp.py
 ```
 ![demo](preview2048.gif)
 
+# LICENSE
+The code is under Apache-2.0 License.