protected virtual void updateParticleProperty(ParticleUnit unit)
 {
     unit.Accelerate = Vector2.Zero;
     foreach (ForceField ff in fields)
     {
         unit.Accelerate.X += ff.GetForceX(unit.Position);
         unit.Accelerate.Y += ff.GetForctY(unit.Position);
     }
     unit.Velocity += unit.Accelerate;
     unit.Position += unit.Velocity;
 }
 protected virtual void newParticlePropertySet(ParticleUnit unit)
 {
     units[particlePointer].Active      = true;
     units[particlePointer].CurrentLife = addParticleLife;
 }