Simple but nice game.
It fits the "expanding" theme very well obviously, and I can't really find something that could be made better or polished, as the game already feels nice to play. Maybe one thing I would suggest is probably adding sounds and music, which are not in the gamr at all (but it doesn't really matter for the jam, as this is a very short jam so it's ok to not have time to implemented sounds, plus the "sound" category is not even in the ratings).
I like the fact that you can basically always win if you go slow, but with the goal being to be very fast, you can then easily lose if you go TOO fast, so you need to find a good compromise between speed and accuracy with your clicks.
Also, the game has a nice gloomy "atmosphere" to it, and for some reason I find the simplistic visuals to be very very clean and amazing to look at (but that may be just me, I love simplistic graphics).
Good work overall, even for this very simple (but challenging) game :D
P.S. my score was 5.79, I couldn't go lower than that without messing it up