kivy/examples/tutorials/pong/main.py

import kivy
kivy.require('1.1.1')

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty, ReferenceListProperty, ObjectProperty
from kivy.vector import Vector
from kivy.factory import Factory
from kivy.clock import Clock


class PongPaddle(Widget):
    score = NumericProperty(0)

    def bounce_ball(self, ball):
        if self.collide_widget(ball):
            vx, vy = ball.velocity
            offset = (ball.center_y-self.center_y)/(self.height/2)
            bounced = Vector(-1*vx, vy)
            vel = bounced * 1.1
            ball.velocity = vel.x, vel.y + offset


class PongBall(Widget):
    velocity_x = NumericProperty(0)
    velocity_y = NumericProperty(0)
    velocity = ReferenceListProperty(velocity_x, velocity_y)

    def move(self):
        self.pos = Vector(*self.velocity) + self.pos


class PongGame(Widget):
    ball = ObjectProperty(None)
    player1 = ObjectProperty(None)
    player2 = ObjectProperty(None)

    def serve_ball(self, vel=(4,0)):
        self.ball.center = self.center
        self.ball.velocity = vel

    def update(self, *args):
        self.ball.move()

        #bounce of paddles
        self.player1.bounce_ball(self.ball)
        self.player2.bounce_ball(self.ball)

        #bounce ball off bottom or top
        if (self.ball.y < self.y) or (self.ball.top > self.top):
            self.ball.velocity_y *= -1

        #went of to a side to score point?
        if self.ball.x < self.x:
            self.player2.score += 1
            self.serve_ball(vel=(4,0))
        if self.ball.x > self.width:
            self.player1.score += 1
            self.serve_ball(vel=(-4,0))


    def on_touch_move(self, touch):
        if touch.x < self.width/3:
            self.player1.center_y = touch.y
        if touch.x > self.width - self.width/3:
            self.player2.center_y = touch.y


Factory.register("PongBall", PongBall)
Factory.register("PongPaddle", PongPaddle)
Factory.register("PongGame", PongGame)


class PongApp(App):
    def build(self):
        game = PongGame()
        game.serve_ball()
        Clock.schedule_interval(game.update, 1.0/60.0)
        return game



if __name__ in ('__android__', '__main__'):
    PongApp().run()