I've been playing now the last few days (really enjoying it, so thanks a lot!) and have a couple small suggestions that I don't see mentioned elsewhere in the thread.
- it would be nice to have a list of the incorrect guesses that you've made. Sometimes I come back after a while and can't remember if I already guessed something or if I just thought about guessing it but wasn't sure... Of course this also dovetails a bit with what some of the other people mentioned about guesses being counted as incorrect even when they're guessed early because then if you have a list of all earlier incorrect guesses then an earlier incorrect guess might now be correct, so I would also change that, that a guess which is only incorrect because it's not available yet isn't counted as incorrect, and instead it says something like "not yet!". Another related problem for me though was I got stuck once and it turned out I had just made a typo in my earlier guess and hadn't noticed, which is why it would be nice to see your earlier guesses. Oh, and also related, I think it counts multiple incorrect guesses of the same word (again not 100% sure since I couldn't see my earlier guesses)
- it would be nice to improve the stats, maybe give you some kind of distribution to see how you're doing, maybe on the calendar you could colour code to show what days you've done well and what days you did worse or something