[zwegner]

I posted this on Twitter last night, but here's my (purported) proof that 4 guesses is optimal: https://gist.github.com/zwegner/508cc183ab94dd27686a40384783...

...and a bit more explanation in the Twitter thread: https://mobile.twitter.com/zwegner/status/148011092775217561...

[salomon812]

Ah, apologizes, I missed your post. This analysis is awesome! I did a single look ahead, so it falls into the -OUCH zone and I have to burn some guesses. Doing the full search across all guesses is key. Well done!