/// <summary>
 /// Check if target unit is in range. If so, apply force and damage
 /// </summary>
 /// <param name="effectPos">origin of effect</param>
 /// <param name="target">target unit</param>
 public void TryApply(Vector2 effectPos, PhysicalBody target, TimeSpan time)
 {
     if (utility.XnaHelper.RectangleIntersectsCircle(target.HitRect, effectPos, _radius))
     {
         tempVec.X = target.Position.X - effectPos.X;
         tempVec.Y = target.Position.Y - effectPos.Y;
         Vector2.Normalize(tempVec);
         float factor = Duration == TimeSpan.Zero ? 1 : (float)time.TotalSeconds / (float)Duration.TotalSeconds;
         target.ApplyForce(_force * factor * tempVec);
         target.ApplyDamage((_damage * factor));
         target.ApplyStatus(_statEffects);
     }
 }
        public virtual void CheckAndApplyUnitCollision(PhysicalBody other)
        {
            if (!Collides)
                return;     //don't check collision if unit shouldn't collide
            //special shattered collision detection
            if (_lifeState == LifeState.Shattered)
            {
                tempRec.Width = _hitRect.Width / c_shatterDivisions;
                tempRec.Height = _hitRect.Height / c_shatterDivisions;
                for (int i = 0; i < c_shatterDivisions ; i++)
                    for (int j = 0; j < c_shatterDivisions; j++)
                    {
                        tempRec.X = (int)(_fragments[i,j].Position.X - tempRec.Width / 2);
                        tempRec.Y = (int)(_fragments[i,j].Position.Y - tempRec.Height / 2);
                        if (tempRec.Intersects(other.HitRect))
                        {
                            Vector2 fVel = _fragments[i, j].Velocity;
                            float fMass = (float)Mass / (c_shatterDivisions * c_shatterDivisions);
                            temp = other.Velocity;
                            other._velocity = (other._velocity * (other.Mass - fMass) + 2 * fMass * fVel) /
                                                (fMass + other.Mass);
                            _fragments[i,j].Velocity = (fVel * (fMass - other.Mass) + 2 * other.Mass * temp) /
                                                (fMass + other.Mass);
                        }
                    }
                return; //ignore normal collision detection
            }

            //check if fire should be transferred
            float dist = XnaHelper.DistanceBetweenRects(HitRect, other.HitRect);
            if (dist < FIRE_SPREAD_DISTANCE)
            {
                if (_statusEffects.Fire > other._statusEffects.Fire)
                {
                    StatEffect transfer = new StatEffect() { Fire = FIRE_SPREAD_FACTOR * dist / FIRE_SPREAD_DISTANCE * _statusEffects.Fire };
                    other.ApplyStatus(transfer);
                    ApplyStatus(transfer * -FIRE_SPREAD_LOSS);
                }
            }

            if (XnaHelper.RectsCollide(HitRect, other.HitRect))
            {
                temp = other._velocity; //temp is a static reusable vector

                other._velocity = (other._velocity * (other.Mass - this.Mass) + 2 * this.Mass * this._velocity) /
                                    (this.Mass + other.Mass);
                this._velocity = (this._velocity * (this.Mass - other.Mass) + 2 * other.Mass * temp) /
                                    (this.Mass + other.Mass);
            }
        }