I have 2 objects, both have a Box collider 2D.

The first object is on the Level1 Sorting Layer and has a Tile script attached to it.

The second object is on the Level0 Sorting Layer and doesn't have any scripts.

The Tile script code is as follows:

void OnMouseDown() { Debug.Log(Input.mousePosition.ToString()); } 

Whenever I click the top tile, nothing prints in the console unless I click on the red area like I show in the image below (red area = [first box collider] minus [the two box colliders intersection area]).

Why this happens ? Why doesn't the OnMouseDown() function fire up simply when you click on its collider, since the top tile is on a higher sorting layer than the bottom tile. How does this work ? Doesn't sorting layer affect the 2D box collider ?