0.4121

This release adds a few career mode interludes!

Career mode now plays a little cutscene after the third and sixth levels. I'd eventually like to have a whole bunch of these, but for now it's just two!

There are also many minor bugfixes and improvements. Decoupling the "cutscenes play before levels" logic from the story mode took a lot of untangling, so please let me know if I broke something!