@Override
    public void reset(){
        valid = false;
        time = 0;
        line_pendulum.setStartX(200);
        line_pendulum.setStartY(200);
        mass = 0;
        circle_pendulum.setCenterX(line_pendulum.getStartX());
        circle_pendulum.setCenterY(line_pendulum.getStartY()); 
        massTextField.clear();
        lengthTextField.clear();
        circle_pendulum.setDisable(false);
    }