The purpose of this weeks Tumblr homework is to leverage animations and gestures to create custom navigation. You should now have the skills to build a large variety of prototypes and manage a larger code base.
Well done completing the required tasks on tabbing between the various view controllers and handling the modal presentation of the compose view.
I'm not sure what's causing the transparency issues in your code: I've looked through manually but you didn't commit your project file to the repo so I can't run the code and look more thoroughly. Perhaps this is something we can look at before class.
/cc @thecodepath