Wow, thank you for the compliment and the constructive feedback!!
I am adding word validation as we speak and hope to have a fresh build deployed sometime soon (probably this evening): https://github.com/benrosen/letter-threader/issues/9
I think your idea for a scoreboard is on the right track. I'm going to start by displaying a (local) all-time high-score next to your current high score while you're playing: https://github.com/benrosen/letter-threader/issues/30
If you have any other feedback or requests, I'm all ears. Thanks for playing!