@Chloe, thank you so much for playing and giving the great feedback.
Future versions of PicPan will have much more variety in mobs (we had 5 planned) better tetris mechanics and tons of things like the scalability you mentioned. In our minds this is a single-note musical piece. While that note is well played and lovely, we have to flesh out the rest of the song.
Thanks again for taking the time and also for putting this whole thing together. Cheers!