def add(self, center_x, center_y, explosion_ind=None):
"""Adds new explosion animation.
Input parameters:
center_x, center_y - absolute center coordinates of animation;
explosion_ind - index of an animation in the list; if None then
the animation is selected randomly (except small explosion)."""
if explosion_ind == None:
explosion_ind = randint(BLAST_EXPLOSION_IND, DOUBLE_EXPLOSION_IND)
explosion = AnimatedSprite(self.images[explosion_ind], self.scr,
self.view_pt, FRAME_COLS, FRAME_ROWS)
explosion.set_center(center_x, center_y)
explosion.repeat = False
self.items.add(explosion)
