Unity: Object is underneath another object but shouldn't be

Question

I have a simple collision detection program. The red object is controlled by the user and the yellow object is always moving up and down:

However, when the objects are supposed to collide, the red object ends up being underneath the yellow object. I wrote code that should destroy the red object on collision. This is a 2D game project, so I'm not sure how that works. They both have 0 set value for Order In Layer field.

Movement code for red object:

using UnityEngine;
using System.Collections;

public class Movement : MonoBehaviour {

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {
        //GetKeyDown checks if a button is clicked, but GetKey checks if a button is held down.

        //LEFT
        if (Input.GetKey (KeyCode.LeftArrow))
        {
            transform.Translate(-1 * Vector2.right);
        }

        //RIGHT
        if (Input.GetKey (KeyCode.RightArrow))
        {
            transform.Translate(Vector2.right);
        }

        //UP
        if (Input.GetKey(KeyCode.UpArrow))
        {
            transform.Translate(Vector2.up);
        }

        //DOWN
        if (Input.GetKey(KeyCode.DownArrow))
        {
            transform.Translate(-1 * Vector2.up);
        }
    }
}

Movement code for yellow object (contains collision event):

using UnityEngine;
using System.Collections;

public class EnemyMovement : MonoBehaviour {

    private bool moveUp;

    // Use this for initialization
    void Start () {
        moveUp = true;
    }

    // Update is called once per frame
    void Update () {

        if(transform.position.y == 30)
        {
            moveUp = false;                               
        }
        else if(transform.position.y == -30)
        {
            moveUp = true;
        }

        if (moveUp) 
        {
            transform.Translate (Vector2.up);
        } 
        else
        {
            transform.Translate (-1 * Vector2.up);
        }
    }

    void OnCollisionEnter (Collision col)
    {
        if(col.gameObject.name == "player_character")
        {
            Destroy(col.gameObject);
        }
    }
}

Also, I'm a complete newbie with Unity, so sorry if I'm asking something that should be obvious.

Answer 1

For Physics2D the method needs to be called OnCollisionEnter2D and both gameobject needs to have a Collider like BoxCollider2D or CircleCollider2D

public class EnemyMovement : MonoBehaviour 
{
    void OnCollisionEnter2D (Collision2D col)
    {
        if(col.gameObject.name == "player_character")
        {
            Destroy(col.gameObject);
        }
    }
}

For Layer Ordering you are already found the correct property Order In Layer. The red object needs to have a higher number i.e. 1 then the yellow object.