def METHOD_NAME(self, delta_time):
    """ Movement and game logic """
    # Calculate speed based on the keys pressed
    self.player_sprite.change_x = 0
    self.player_sprite.change_y = 0
    if self.up_pressed and not self.down_pressed:
        self.player_sprite.change_y = PLAYER_MOVEMENT_SPEED
    elif self.down_pressed and not self.up_pressed:
        self.player_sprite.change_y = -PLAYER_MOVEMENT_SPEED
    if self.left_pressed and not self.right_pressed:
        self.player_sprite.change_x = -PLAYER_MOVEMENT_SPEED
    elif self.right_pressed and not self.left_pressed:
        self.player_sprite.change_x = PLAYER_MOVEMENT_SPEED
    # Call update on all sprites (The sprites don't do much in this
    # example though.)
    self.physics_engine.update()
    # Scroll the screen to the player
    self.scroll_to_player()