This is such a simple but awesome game idea. The result is fun and addictive.
At first I didn't understand, that I had finished the first level and have to press C. Maybe make the (C)ontinue more visible when it appears or put a message in the middle of the screen. And use more common keys, maybe space for spread and enter or any key for continue?
But that's just nit picking, this game is beautiful and well polished. And now excuse me, I have to continue playing it :-D