Awesome idea! Some of the bigger levels were extremely stressful! Could've used some music, and more sound effects.
I'd love to have music in the game, but every time I try making some, it ends up sounding horrible. :/
It's alright to use public domain music and sounds from online sources, for example: OpenGameArt, FreeSound. I don't want to post external links here, but both sites end in .org
