My collison isn't working regardless of what tutorial I use.

Questions & Answers
1

Whenever I go back into Unity I get the error:
Assets\Bullet.cs(14,13): error CS0120: An object reference is required for the non-static field, method, or property ‘enemyHP.takeDamageEnemy(int)’

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enemyHP.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class enemyHP : MonoBehaviour
{
    
    public int curEnemyHP = 100;
    public int maxEnemyHP = 100;

    void Start()
    {
        curEnemyHP = maxEnemyHP;
    }

    public void takeDamageEnemy(int damage) {
        curEnemyHP -= damage;
        if (curEnemyHP <= 0) {
            Destroy(gameObject);
        }
    }

}

Bullet.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Bullet : MonoBehaviour
{

    void OnCollisionEnter2D(Collision2D collision) {
        Destroy(gameObject);
    }

    void OnTriggerEnter2D(Collider2D other) {
        if (other.gameObject.tag == "enemy") {
            enemyHP.takeDamageEnemy(20);
        }
    }

}
2

@joshthekillerguineapig Make sure both your objects have colliders that both have isTrigger checked, (since you are using OnTriggerEnter2D) and I think you need a rigidbody on both of the objects. If you want to use OnCollisionEnter2D I think you do exactly as I just explained, but without checking isTrigger.

Hope this helps!