kivy pongball class

1class PongBall(Widget):
2
3    # velocity of the ball on x and y axis
4    velocity_x = NumericProperty(0)
5    velocity_y = NumericProperty(0)
6
7    # referencelist property so we can use ball.velocity as
8    # a shorthand, just like e.g. w.pos for w.x and w.y
9    velocity = ReferenceListProperty(velocity_x, velocity_y)
10
11    # ``move`` function will move the ball one step. This
12    #  will be called in equal intervals to animate the ball
13    def move(self):
14        self.pos = Vector(*self.velocity) + self.pos
15