Yes, the game allows for clicking one fish more than once and the number of fishes will gradually increase when this happens over and over. This can be easily triggered with multiple mouses (or one mouse plus mouse keys, as I had).
1. Rather than waiting for the game engine update callback, I handle touch/mouse input immediately (required by SpeechSynthesis) so multiple input events can trigger before the game engine cleans up a destroyed object (fish).
2. I incremented score synchronously but marked a fish as destroyed asynchronously so there was a window where another click on the fish could occur.
Thanks again!