1. You will also need to ensure each platform agent has an assigned brain. In this example, each platform agent was created using a prefab. To update all of the brains in each agent at once, you only need to update the platform agent prefab. In the **Project** window, go to the `Assets/ML-Agents/Examples/3DBall/Prefabs` folder. Expand `Game` and click on the `Platform` prefab. You should see the `Platform` prefab in the **Inspector** window. In the **Project** window, drag the **3DBallLearning** Brain located in `Assets/ML-Agents/Examples/3DBall/Brains` into the `Brain` property under `Ball 3D Agent (Script)` component in the **Inspector** window.
**Note**: The Unity prefab system will modify all instances of the agent properties in your scene. If the agent does not synchronize automatically with the prefab, you can hit the Revert button in the top of the ***Inspector*** window.
**Note**: The Unity prefab system will modify all instances of the agent properties in your scene. If the agent does not synchronize automatically with the prefab, you can hit the Revert button in the top of the ***Inspector*** window.
**Note:** Assigning a Brain to an agent (dragging a Brain into the `Brain` property of
**Note:** Assigning a Brain to an agent (dragging a Brain into the `Brain` property of
the agent) means that the Brain will be making decision for that agent. Whereas dragging
a Brain into the Broadcast Hub means that the Brain will be exposed to the Python process.
The `Control` checkbox means that in addition to being exposed to Python, the Brain will
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