gravity = 0.0001

class QueenSprite:

    def __init__(self, img, target_posn):
        self.image = img
        self.target_posn = target_posn
        (x, y) = target_posn
        self.posn = (x, 0)     # Start ball at top of its column
        self.y_velocity = 0    #    with zero initial velocity

    def update(self):
    self.y_velocity += gravity
    (x, y) = self.posn
    new_y_pos = y + self.y_velocity
    (target_x, target_y) = self.target_posn   # Unpack the position
    dist_to_go = target_y - new_y_pos         # How far to our floor?

    if dist_to_go < 0:                        # Are we under floor?
        self.y_velocity = -0.65 * self.y_velocity     # Bounce
        new_y_pos = target_y + dist_to_go     # Move back above floor

    self.posn = (x, new_y_pos)                # Set our new position.

    def draw(self, target_surface):      # Same as before.
        target_surface.blit(self.image, self.posn)