That reminds me... I asked the book before starting the jam, "How should I approach the Public Domain Game Jam?" Its response was hexagram 48: The Well with the top line changing. It represents a well with its surface water in motion. It's a great metaphor for the public domain, which is a well of information, somewhat buried in time, and with the surface moving, it means we're drawing from the part available to us.
If you're interested in the content, I've read the book itself thinks it should be used more often because it still has a lot of useful wisdom to share.
@Six Down Studios: Thanks for your feedback! I'm glad you found it strange. I think it's even more strange that we expect games we've never played to be familiar.