Calculate the normal of a collider

I have a 2D game with two objects - the player (a circle) and rectangle (which can be rotated at any angle). The player can collide with this rectangle.

How can I calculate the normal line of the collider (by which I mean the angle at which the player hits the rectangle)?

Thanks

You don’t need to calculate it - it’s given to you in the Collision2D object passed to OnCollisionEnter2D: Unity - Scripting API: ContactPoint2D.normal