# Create a custom brush that runs a script

> Create a prebuilt or custom scriptable brush that draws in more ways than the default tile palette tools.

Scriptable brushes are brushes that can draw in more ways than the default toolbar, for example draw a line of tiles or random tiles. Scriptable brushes are part of the [2D Tilemap Extras package](https://docs.unity3d.com/Packages/com.unity.2d.tilemap.extras@latest/index.html?subfolder=/manual/).

You can do the following:

* Use a prebuilt scriptable brush.
* Create a custom scriptable brush using the `GridBrushBase` API.

## Use a prebuilt scriptable brush

To use a prebuilt scriptable brush, follow these steps:

1. Make sure the 2D Tilemap Extras package is installed in your project. For more information, refer to [set up your project for 2D games](/engine/6000.3/manual/unity2d/2d-game-development/setup-project-2d-game.md).
2. Select a tile from the tile palette as normal.
3. In the **Brush** section, select a brush type other than **Default Brush**.

For more information about each scriptable brush, refer to [Scriptable brushes](https://docs.unity3d.com/Packages/com.unity.2d.tilemap.extras@latest/index.html?subfolder=/manual/Brushes.html) in the 2D Tilemap Extras package documentation.

## Create a custom scriptable brush

1. To create a new C# script, from the main menu select **Assets** > **Create** > **MonoBehaviour script**.

2. Open the script and replace the code with a class that inherits from `UnityEngine.Tilemaps.GridBrushBase`. For example:

   ```csharp
   using UnityEngine;
   using UnityEngine.Tilemaps;

   public class MyCustomBrush : GridBrushBase
   {
   }
   ```

3. Implement the methods of [`GridBrushBase`](/engine/6000.3/script-reference/unityengine/gridbrushbase.md) to define the behavior of the brush. For example, implement the following:

   * `Paint` to add items to the grid.
   * `Erase` to remove items from the grid.
   * `FloodFill` to fill areas on the grid.
   * `Rotate` to rotate items.
   * `Flip` to flip items.
   * `ChangeZPosition` and `ResetZPosition` to control the 3D height of items in an Isometric Z as Y tilemap.

4. To create instances of your brush as assets in your project, add the `CreateAssetMenu` attribute before the class declaration.

   ```csharp
   using UnityEngine;
   using UnityEngine.Tilemaps;

   [CreateAssetMenu]
   public class MyCustomBrush : GridBrushBase
   {
       // ...
   }
   ```

5. Create an instance of the brush. For example in the previous example, from the main menu, select **Assets** > **My Custom Brush**.

The custom brush automatically appears in the **Brush Inspector** dropdown in the **Tile Palette** window. For more information, refer to [Tile Palette window reference](/engine/6000.3/manual/unity2d/tilemaps/create-tile-palette/tile-palette-editor-reference.md).

### Create a custom editor for a scriptable brush

You can also make a custom editor for a custom scriptable brush. This works the same way as custom editors for scriptable objects. The following are the main methods you would want to override when creating a custom editor:

* Override `OnPaintInspectorGUI` to have an Inspector window appear on the Palette when the Brush is selected to provide additional behaviour when painting.
* Override `OnPaintSceneGUI` to add additional behaviours when painting on the `SceneView`.
* Override `validTargets` to have a custom list of targets which the Brush can interact with. This list of targets is shown as a dropdown list in the Palette window.
* Add a `CustomGridBrush` attribute to your Scriptable Brush class to change its name, make it the default brush in the project, and other options.
* Add a `BrushTools` attribute to your class with a list of compatible `TilemapEditorTools` types. This ensures that your Scriptable Brush only activates with these specific tools from the Tile Palette toolbar.

## Examples

Refer to the following for examples of a custom scriptable brush:

* [`GridBrushBase`](/engine/6000.3/script-reference/unityengine/gridbrushbase.md) in the API documentation for a simple example that paints GameObjects instead of tiles.
* Select a prebuilt scriptable brush in the **Tile Palette** window, then double-click the **Script** field to open the script and check how the brush is implemented.

## Additional resources

* [Create a custom tile that runs a script](/engine/6000.3/manual/unity2d/tilemaps/custom-tiles-brushes/scriptable-tiles.md)