Got the five rooms of the castle laid out, as well as the four bosses leading up to the final boss wired up and ready to go. Added some narrative bits to bring the story full circle (although I think I need to go back and modify some of the dialogue I have already, because the stuff I wrote today hinges on knowing something about the general lore and I don't think I clarified it beforehand).
Even in my exhaustion from substitute teaching (which went well, thank you), I managed to get all of that done. Tomorrow is the final boss, ending cutscene, and however I'm going to do the credits. Then its just editing and testing!