title: showing admob interstitial every x play unity
body: <p>I am trying to make my interstitial admob ad appear when a user enters the map for the third time.
  My code is:</p>
  
  <pre><code>using UnityEngine;
  using System.Collections;
  using GoogleMobileAds;
  using GoogleMobileAds.Api;
  
  public class interstitial_ad : MonoBehaviour {
  
      private InterstitialAd interstitial;
  
      void Start()
      {
          interstitial = new InterstitialAd ("ca-app-pub-xxx");
          interstitial.LoadAd (new AdRequest.Builder ().Build ());
      }
      void Update()
      {
          if (interstitial.IsLoaded())
          {
              interstitial.Show();
          }    
      }
  }
  </code></pre>
  
  <p>It shows the ad every time I enter the map, so I tried to add:</p>
  
  <pre><code>playCount++;
          if (playCount % 3 == 0) {
  </code></pre>
  
  <p>but that did not work for me, probably because of the void Update() part. Do you have any ideas/hints how to make it work?</p>