I loved this, it's so cute!
I think it just got stuck when there are no balls left. I had to refresh the page. (EDIT: I missed the part about pressing esc to go back to the menu, oops. That's on me.)
Also, sometimes the cats can get stuck between the peg and the edge of the board (happened on the right side for me.), meaning they never score. I think this can be fixed by making the board just a wee bit wider on the side.
But I still enjoyed it a lot. The cute music and graphics, along with the silliness of the tumbling cats, really made it a fun distraction. Thanks for making this. :)