public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.hitObjectsCollisionGroupStrings.Contains("gift"))
     {
         hasCollectedGift = true;
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.hitObjectsCollisionGroupStrings.Contains(UnpassableBlock.CollisionGroupString)|| collisionData.hitObjectsCollisionGroupStrings.Contains(Racket.CollisionGroupString))
     {
         base.RespondToCollision(collisionData);
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.hitObjectsCollisionGroupStrings.Contains(UnstoppableBall.CollisionGroupString))
     {
         this.IsDestroyed = true;
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.hitObjectsCollisionGroupStrings.Contains("indestructibleBlock") || collisionData.hitObjectsCollisionGroupStrings.Contains("racket"))
     {
         base.RespondToCollision(collisionData);
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.hitObjectsCollisionGroupStrings[collisionData.hitObjectsCollisionGroupStrings.Count - 1] == "gift")
     {
         this.isShootingRacket = true;
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.HitObjectsCollisionGroupStrings[0] == "indestructibleBlock" ||
         collisionData.HitObjectsCollisionGroupStrings[0] == "racket")
     {
         base.RespondToCollision(collisionData);
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     foreach (var c in collisionData.hitObjectsCollisionGroupStrings)
     {
         if ((c==UnpassableBlock.CollisionGroupString) || (c==Racket.CollisionGroupString))
             base.RespondToCollision(collisionData);
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     if (collisionData.hitObjectsCollisionGroupStrings[0] == IndestructibleBlock.CollisionGroupString ||
         collisionData.hitObjectsCollisionGroupStrings[0] == Racket.CollisionGroupString)
     {
         base.RespondToCollision(collisionData);
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     List<string> collisionObjects = collisionData.hitObjectsCollisionGroupStrings;
     if (collisionObjects.Contains(IndestructibleBlock.CollisionGroupString) ||
         collisionObjects.Contains(Racket.CollisionGroupString))
     {
         base.RespondToCollision(collisionData);
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     // the following code gives possibility an Unpassable Block to be destroyed by Explosion Block's Explosion Object!
     foreach (string colisionObj in collisionData.hitObjectsCollisionGroupStrings)
     {
         if (colisionObj == ExplodingObject.CollisionGroupString)
                  base.RespondToCollision(collisionData);
     }
 }

     public override void RespondToCollision(CollisionData collisionData)
     {
         //This ball should change direction only if it hits indestructible wall or user's racket
         if (collisionData.hitObjectsCollisionGroupStrings.Contains(UnpassableBlock.CollisionGroupString) ||
 collisionData.hitObjectsCollisionGroupStrings.Contains(Racket.CollisionGroupString))
         {
             base.RespondToCollision(collisionData);
         }
     }

        public override void RespondToCollision(CollisionData collisionData)
        {
            base.RespondToCollision(collisionData);

            if (collisionData.hitObjectsCollisionGroupStrings.First() == "gift")
            {
                shooting = true;
            }
        }

 public override void RespondToCollision(CollisionData collisionData)
 {
     foreach (string collosionObject in collisionData.hitObjectsCollisionGroupStrings) 
     {
         if (collosionObject == "racket") 
         {
             this.IsDestroyed = true;
         } 
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     foreach (var collisionObjectString in collisionData.hitObjectsCollisionGroupStrings)
     {
         if (collisionObjectString == "unstoppable ball")
         {
             this.IsDestroyed = true;
         }
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     foreach (string item in collisionData.hitObjectsCollisionGroupStrings)
     {
         if (item.Equals("indestructibleBlock") || (item.Equals("unpassableBlock") || item.Equals("racket")))
         {
             base.RespondToCollision(collisionData);
         }
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     for (int i = 0; i < collisionData.hitObjectsCollisionGroupStrings.Count; i++)
     {
         if (collisionData.hitObjectsCollisionGroupStrings[i] != "block")
         {
             base.RespondToCollision(collisionData);
         }
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     for (int i = 0; i < collisionData.hitObjectsCollisionGroupStrings.Count; i++)
     {
         if (collisionData.hitObjectsCollisionGroupStrings[i] != "ball")
         {
             this.IsDestroyed = true;
         }
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     foreach (var item in collisionData.hitObjectsCollisionGroupStrings)
     {
         if (item == "UnstoppableBall")
         {
             this.IsDestroyed = true;
         }
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     for (int i = 0; i < collisionData.hitObjectsCollisionGroupStrings.Count; i++)
     {
         if (collisionData.hitObjectsCollisionGroupStrings[i] == "unpassableBlock" || collisionData.hitObjectsCollisionGroupStrings[i] == "racket")
         {
             base.RespondToCollision(collisionData);
         }
     }
 }

 public override void RespondToCollision(CollisionData collisionData)
 {
     foreach (string collisionObject in collisionData.hitObjectsCollisionGroupStrings)
     {
         if (collisionObject == "gift")
         {
             this.bulletsLeft += Gift.BulletsBonus;
         }
     }
 }