void frame_MouseOver(Element sender, MouseEventArgs e)
{
var pcur = new Vector2(e.CurrentMouseState.X, e.CurrentMouseState.Y);
var pold = new Vector2(e.PreviousMouseState.X, e.PreviousMouseState.Y);
if (mactive)
{
PE.AddInstantaneousForceField(new InstantaneousForceField(pcur, rad, DefaultForces.GenerateDirectionalField(400 * (pcur - pold), rad)));
}
}