# Collisions and interactions in the Physics Core 2D API

> Enable and detect collisions between 2D physics objects, and cast rays to check for intersections.

Combine or connect shapes, and enable and detect contact between physics objects using the Physics Core 2D API.

> **Note:**
>
> This documentation is about writing C# scripts using the `Unity.U2D.Physics` API. To use 2D physics in the Unity Editor using components like the Rigidbody 2D component, refer to [2D physics](/engine/6000.6/manual/unity2d/2d-physics.md.md) instead.

| **Topic**                                                                                                                         | **Description**                                                                                              |
| --------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| [Introduction to collision in the Physics Core 2D API](/engine/6000.6/manual/unity2d/2d-physics-api/interactions/introduction.md) | Learn about collisions between 2D physics objects, including collision types, layers, and layer masks.       |
| [Configure collisions between objects](/engine/6000.6/manual/unity2d/2d-physics-api/interactions/collisions-enable.md)            | Change which objects collide with which using layers and masks, and enable using 64 layers instead of 32.    |
| [Detect collisions between objects](/engine/6000.6/manual/unity2d/2d-physics-api/interactions/collision-handle.md)                | To detect when collisions occur and respond to them, use collision callback methods or event methods.        |
| [Check Physics Core 2D API intersections](/engine/6000.6/manual/unity2d/2d-physics-api/interactions/raycasting.md)                | To check whether 2D physics objects overlap or will collide, also known as intersections, use query methods. |

## Additional resources

* [Optimize the Physics Core 2D API with multithreading](/engine/6000.6/manual/unity2d/2d-physics-api/multithreading.md)
* [PhysicsCore2D repository](https://github.com/Unity-Technologies/PhysicsExamples2D/tree/master) on GitHub