BoomGoesblock.cs

using UnityEngine;
using System.Collections;

public class BoomGoesBlock : MonoBehaviour {
	public static int amount = 0;
	private GameObject go;

	// Use this for initialization
	void Start () {
		go = this.gameObject;
	}

	void OnCollisionEnter2D(Collision2D col)
	{
		if(amount < 70 && !col.gameObject.GetComponent<BoomGoesBlock>() && !(transform.localScale.x < 0.5f))
			SpawnMore ();
	}

	void SpawnMore()
	{
		for (int i = 0; i < 4; i++) 
		{
			amount++;
			GameObject newGo = Instantiate (go, transform.position, Quaternion.identity) as GameObject;
			newGo.transform.localScale = go.transform.localScale/ 2;
			newGo.GetComponent<Rigidbody2D> ().AddForce(new Vector2(Random.Range(-100,100),Random.Range(100,300) * 2));
		}

		Destroy (go);
	}

}