Yep, I broke my blog.
I was looking at the new "template designer" and following Google's (typically) worse than useless instructions. I misunderstood what they were telling me to do and nuked my old template and all its settings. There was no way to revert, so I tried to go back to the old template. That was a dismal failure—it was way back to the beginning with nothing but the basic basics.
So, I went back to the template designer. This temporary look is just a standard (new) template with my old elements restored (like the all-important "what time is it" widgets…). After spending an hour and a half trying to fix my blog, I decided to give up for tonight. Maybe I'll have some time over the weekend.
However, each post now has four ways to share—a new feature which is the whole reason I was looking at the template designer in the first place (they're not compatible with old templates). Share if you want to.
So, consider this to be a work in progress. I planned on upgrading, actually; I just hadn't planned on doing it this way.