# Physics Simulation World asset reference

> Explore the properties you can use to configure a Physics Simulation World asset in the Unity Editor using 2D Physics Core.

Explore the properties you can use to create a simulation world using 2D Physics Core.

> **Note:**
>
> This documentation is about using Pose, Area, and Constraint components. To use 2D physics in the Unity Editor using components like the Rigidbody 2D component, refer to [2D physics](/engine/6000.7/manual/unity2d/2d-physics.md.md) instead.

## Physics Simulation World asset properties

| **Property**   | **Description**                                                                                                                                                                                                                                                                              |
| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Definition** | Sets the Physics Simulation Definition asset that contains the world's settings, such as gravity. Drag a Physics Simulation Definition asset from the **Project** window to this property, or select the picker (**⊙**). If this property is empty, the world uses Unity's default settings. |
| **Make Asset** | Creates a Physics Simulation Definition asset for you to save, then assigns it to the **Definition** property. This property is available only if **Definition** is empty.                                                                                                                   |

## User Data

Use the properties in this section to add your own data to the component, and read it using the `U2D.Physics` API. For more information, refer to [Add custom data to a 2D Physics Core object](/engine/6000.7/manual/unity2d/2d-physics-api/properties/custom-data.md.md).

| **Property**     | **Description**                                                                                                                                                                                                             |
| ---------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Object**       | Sets a custom object. Drag any object from the **Hierarchy** or **Project** windows to this property, or select the picker (**⊙**).                                                                                         |
| **Physics Mask** | Sets a custom set of enabled and disabled layers. For more information, refer to [Configure collisions between 2D Physics Core objects](/engine/6000.7/manual/unity2d/2d-physics-api/interactions/collisions-enable.md.md). |
| **Float**        | Sets a custom floating-point number.                                                                                                                                                                                        |
| **Int**          | Sets a custom integer.                                                                                                                                                                                                      |
| **Int 64**       | Sets a custom 64-bit integer.                                                                                                                                                                                               |
| **Vector 3 Int** | Sets a custom 3D vector of integers.                                                                                                                                                                                        |
| **Bool**         | Sets a custom Boolean value.                                                                                                                                                                                                |

## Additional resources

* [Create multiple simulation worlds with 2D Physics Core](/engine/6000.7/manual/unity2d/2d-physics-api/worlds/world.md)
* [Physics Simulation Definition asset reference](/engine/6000.7/manual/unity2d/2d-physics-api/worlds/reference-world.md)
* [Physics Simulation component reference](/engine/6000.7/manual/unity2d/2d-physics-api/worlds/reference-simulation-component.md)
* [Physics Pose component reference](/engine/6000.7/manual/unity2d/2d-physics-api/create-objects/reference-body.md)
* [Configure global 2D Physics Core settings](/engine/6000.7/manual/unity2d/2d-physics-api/properties/class-physics-core-settings2d.md)