Really great base for what seems to be a very ambitious platformer than I hope you guys work on! After reading the GDD man I really wish you guys had got in even some of those things because as is the game functions but is rather barebones, and a version with what you guys have suggested would be really cool.
I will also say that when it comes to finishing the level, maybe when they've reached the "completion" thresh-hold, pan over the whole level to show what a colourful marvel the player has created, just a suggestion though I think it'd be cool.
All in all, really cool game and I do really hope you guys keep working on this.