How do I get a spike to kill the player in 2D unity

Collisions between objects can be detected via the OnCollisionEnter2D() function. To set this up:

1. Make sure that both your player and the spike have a Collider2D component on them. There are different types of colliders for different shaped objects.

2. Assign some sort of identifier to the player and the spikes so that we can quickly detect what kind of object we are colliding with. Usually this is done via tags or layers.

3. Set up your OnCollisionEnter2D function. Decide whether you want the player to be responsible for detecting the spikes or vice versa. Then put a script on the object that you have chosen and implement the OnCollisionEnter2D function. Here's a very basic example:

   ---

   public class SpikeDamage : MonoBehaviour{

      //This script is designed to be attached to your spike gameobject
    
            //This function will be called every time we touch another collider
            //If you are using a collider with the "IsTrigger" option selected, use OnTriggerEnter2D instead
            void OnCollisionEnter2D(Collider2D col){
                //When this is called, it will give us the collider we touched as a parameter
                //We can touch lots of different colliders, so before we try to deal damage lets check what we are colliding with
                //This assumes that the player gameobject has been given a tag called "Player"
                if(col.CompareTag("Player")){
                    //If we are colliding with the player, then you can now deal damage.
                    //Do this however you want. Usually you will want to access some component on the player gameobject, then call a function that deals damage.
                    col.GetComponent<PlayerHealth>().DealDamage(100);
                }
            }
        }