I really like this, it kind of reminds me of "Hangman"!

A few ideas, if you don't mind:

1. Have a "normal" mode and "master" mode, where the normal mode has words with maybe 5 letters and the master mode uses 7 letters

2. Have an archive of previous games - kinda sucks that I can't play the old ones!

3. Contrast on the up/down arrows on letters isn't clear enough, at least not for me (colour blind)