Got one in. Struggled to think of a story, then promptly wrote myself into a corner. Ended up stuck there for a couple weeks, was getting increasingly worried I'd squander this opportunity to get writing feedback!
Finally, while sitting in a dark hotel room in Tijuana a couple days ago, the answer came to me and I finished up. As always, my first draft went a couple hundred words over the limit and as usual, they were all gooooooold but I somehow managed to make it work. I mean word-count-wise, not necessarily that it's a good story. But it's 500 DAMN WORDS, who needs definitive articles, pronouns, and verbs anyhow? Crutches, the lot of them!