public static void Main(string[] args)
        {
            var creatures = new BadCreature[100];

            foreach (var c in creatures)
            {
                c.X++; // not memory-efficient
            }

            var creatures2 = new Creatures(100);

            foreach (var c in creatures2)
            {
                c.X++;
            }
        }
 public Creature(Creatures creatures, int index)
 {
     this.creatures = creatures;
     this.index     = index;
 }