Most jam games are super hard and/or difficult to understand =)
This one has a basic and efficient gameplay, and starts easy, so it's really a nice beginning! Though, like Narkhos said earlier, it would be cool to spice things up after a while. Having things go faster each minute or whatever could give an end to each game with a relevant score (otherwise the player will just quit if it seems to easy and endless).
Good job! Hope you'll update it a bit :)