You've got a pretty cute story with some nice and simple graphics to boot. I also like the sounds you made, they're very unique and they fit the game pretty well. I really like the red guy's mechanic of making platforms, it makes the platforming more fun and there's quite a bit of skill involved in it too.
I think some checkpoints could be placed better. Some deaths set you way too far back, particularly the section with the wind. I also think the player hitbox should be smaller, because there were some places where you needed super precise jumping to fit through one block wide gaps. Finally, the bubble and platform projectiles should move a bit faster so that the player doesn't have to wait as long to continue on.
Great job on your game, I spent a while playing it.