You must have hurt his feelings by doing so. Give him some time to recover. Teenagers tend to associate these little victories to great emotions due to their hormones that are out of place. In such situations when your child is busy playing;
1. First, tell him that you want him to wind-up in some time.
2. Then if he does not complete within the given time, warn him once again and tell him that you would switch off the game in some time.
3. If he exceeds the limit, then switch off the game. This method would give him some time to process and be prepared for the consequence.