def METHOD_NAME(self, key, _):
    """Called whenever a key is pressed. """
    if key == arcade.key.UP:
        self.player_sprite.change_y = MOVEMENT_SPEED
    elif key == arcade.key.DOWN:
        self.player_sprite.change_y = -MOVEMENT_SPEED
    elif key == arcade.key.LEFT:
        self.player_sprite.change_x = -MOVEMENT_SPEED
    elif key == arcade.key.RIGHT:
        self.player_sprite.change_x = MOVEMENT_SPEED