I've been working on-and-off on a dark mode, but it's slow since this project is kind of "finished" on my todo list :) I'd love to have sounds but didn't have the time yet. If you want to collaborate, I'd be happy to add your sounds!
You should not get soft-locked at all, that's a bug. Do you remember the cards you had and how you got into that situation? I might have to add a game over condition to catch this, but in general it shouldn't happen.