1) Sound was something I started thinking about early on, but a combination of not really having any good ideas for it and a lack of time meant it wasn't in the final game. I didn't have any real ideas for how sound effects would work for a game like this, and after my submission last year, I wasn't really happy with the idea of having music without sound effects. As I was running out of time and needed sleep, I decided to focus on other parts of the game, such as the title and win screens, instead of finding and adding BG music. I've gotten enough comments on it that I probably won't make the same choice next year, but I don't think I made the wrong choice for this game.
2) Having things pop off was something I considered while conceptualizing the game. Unlike the sticking mechanic, which I figured wouldn't be too difficult to program, deciding what should pop off to not leave gaps and where they should fly to was a problem I didn't feel comfortable trying to tackle alone in a limited time. I decided early on that I wasn't going to spend time trying to do it, and instead try to focus on making the core of having things stick feel good (with things like the camera zooming and re-centering and the controls adjusting to the new size).