Rotating

my.kv

<MyGame>:
    FloatLayout:
        size: self.parent.width, self.parent.height
        MyWidget:
            id: widget
            pos_hint: {'x': 0, 'y': .5 }

<MyWidget>:
    canvas.before:
        PushMatrix
        Rotate:
            angle: self.angle
            axis: 0, 0, 1
            origin: self.x, self.y
    canvas:
        Ellipse:
            pos: self.x + 10, self.y - 5
            size: 30, 10
    canvas.after:
        PopMatrix
        Ellipse:
            pos: self.x - 10, self.y - 10
            size: 20, 20

rotate.py

__author__ = 'michael hughes'

import kivy
# require at least kivy 1.8
kivy.require('1.8.0')

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty
import math


class MyWidget(Widget):

    angle = NumericProperty(0)

    def on_touch_down(self, touch):
        radians = math.atan2(touch.y - self.parent.center_y, touch.x)
        self.angle = math.degrees(radians)


class MyGame(Widget):
    pass

class MyApp(App):

    def build(self):
        """Build creates the root game object
        and starts it
        """
        game = MyGame()
        return game

if __name__ == '__main__':
    MyApp().run()