public override void OnDetached(AbstractEntity entity)
        {
            (entity as Entity).OnUpdate -= OnUpdate;
            entity.GetProperty <CollisionProperty>("collision").OnContact -= CollisionHandler;
//            ((Vector3Attribute)entity.GetAttribute("repulsion_velocity")).ValueChanged -= RepulsionChangeHandler;
            entity.GetAttribute <StringAttribute>("repulsed_by").ValueChanged    -= RepulsedByChangeHandler;
            entity.GetAttribute <IntAttribute>("players_on_island").ValueChanged -= PlayersOnIslandChangeHandler;
        }
        public override void OnAttached(AbstractEntity entity)
        {
            Debug.Assert(entity.HasVector3(CommonNames.Position));

            this.island          = entity as Entity;
            this.constants       = Game.Instance.Simulation.EntityManager["island_constants"];
            this.playerConstants = Game.Instance.Simulation.EntityManager["player_constants"];

            if (!entity.HasAttribute(CommonNames.MaxHealth))
            {
                entity.AddFloatAttribute(CommonNames.MaxHealth, (entity.GetVector3(CommonNames.Scale).Length() * constants.GetFloat("scale_health_multiplier")));
            }
            entity.AddFloatAttribute(CommonNames.Health, entity.GetFloat(CommonNames.MaxHealth));

            hasFixedMovementPath = entity.GetBool("fixed");

            entity.AddVector3Attribute("repulsion_velocity", Vector3.Zero);
            entity.AddVector3Attribute("pushback_velocity", Vector3.Zero);
            entity.AddVector3Attribute("repositioning_velocity", Vector3.Zero);

            entity.AddStringAttribute("repulsed_by", "");
            entity.AddIntAttribute("players_on_island", 0);
            entity.AddIntAttribute("players_targeting_island", 0);

            // approximation of island's radius and height
            Vector3 scale = island.GetVector3(CommonNames.Scale);

            entity.AddFloatAttribute("height", scale.Y);
            scale.Y = 0;
            entity.AddFloatAttribute("radius", scale.Length());

            (entity as Entity).OnUpdate += OnUpdate;

            entity.GetProperty <CollisionProperty>("collision").OnContact += CollisionHandler;
//            ((Vector3Attribute)entity.GetAttribute("repulsion_velocity")).ValueChanged += RepulsionChangeHandler;
            entity.GetAttribute <StringAttribute>("repulsed_by").ValueChanged    += RepulsedByChangeHandler;
            entity.GetAttribute <IntAttribute>("players_on_island").ValueChanged += PlayersOnIslandChangeHandler;

            originalPosition = entity.GetVector3(CommonNames.Position);
        }