Detecting Collision for DanmakU?

Hi,

I'm using the DanmakU Package from https://github.com/james7132/DanmakU .
It's pretty good, but I have no idea how to set up collision.

I added a User Layer called Bullet and have this attached to the player

Code (CSharp):

1. void OnCollisionEnter2D(Collision2D col)
2.     {
3.      
4.         if (col.gameObject.layer == 12)
5.         {
6.              Debug.Log("I'VE BEEN HIT UGHHH");
7.         }
8. }

... but it's not working.
I attached an img of the Physics layers.

Is there maybe a problem with the way I set up the Physics Layers Collision?
---
I think the emitter is spawning Danmaku Prefabs so I attacked a Circle Collider but nothing's happening.

Any help greatly appreciated! Thank you.

 

I've never used the LayerCollisionMatrix before. Don't quite understasnd why its only for 3D. Any resources you recommend? (https://docs.unity3d.com/Manual/LayerBasedCollision.html)

If the matrix is for collision between two objects and their layers why is it for 3D?

Thank you.