My parents once told me of an old pharmacy professor who used to grade on the same scale. If one of their problems had an error, they weren't given partial points but rather met with a "zero". The reason: "you killed the patient". It's an all-or-nothing idea. Maybe that's why mastery grading seems to work me. As much as it's sometimes gratifying to take points off if students are less than perfect, what we're really trying to do is assess if they "get" a given concept. Typically, these types of things are all or nothing.
So have a safe evening Baldwin. Enjoy the win, the snow, the show, and project....or enjoy none of them because they don't exist. By this time tomorrow, the choice will be made.