beat-td/Assets/Scripts/DepthFromY.cs

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

public class DepthFromY : MonoBehaviour {

    private SpriteRenderer spriteRenderer;

	void Update () {
        spriteRenderer = gameObject.GetComponent<SpriteRenderer>();
        spriteRenderer.sortingOrder = Mathf.CeilToInt(-transform.position.y * 100);
	}

}