Otherwise fun game has a bug

Game: "A Christmas Cat"
Author: Bart Bonte (bontegames.com)
Link to game: http://bartbonte.com/christmascat/

The object is to find twenty balls spilled on the floor and various other places by a rambunctious cat who knocked over the Christmas tree.  Upon finding the twentieth ball, an animation plays congratulating the player for completing the game and wishing him/her a happy holiday.

Except that it doesn't, for me at least.

The following four screenshots clearly show the game has been completed, the 20th ball has been found, yet the game just sits there blithely waiting for me to find ball #21.  I can move from room to room (this shouldn't be possible at this point!), I can still manipulate objects in the rooms, and the game does not ever recognize that it is over and I have won.

WARNING: THESE SCREENSHOTS CONTAIN SPOILERS!  If you do not wish to see spoilers before playing the game, stop reading now and go play the game!  You can always come back to this later.

(spoilers below)

 #1) Immediately after clicking the 20th ball.
It should be playing a short animation at this point,
instead of waiting for me to continue the game.

#2) The next room (this shouldn't be possible!)

#3) Nor should this!

#4) Or this!

I might add that this is running on Ubuntu (Linux) v14.04.3, Firefox 42.0 with all extensions disabled.  I've tried it in Chrome on the same computer/OS, and it works properly there.