Nice idea, nice game. Somewhat annoying to have to backtrack so far to get to the right previous word, and a bit 'same-ish' after the first 50 words or so.
Despite comments below there are no hard words. Iron is reached by icon and coin, quiz by quit and suit. I was expecting later words would be harder, but it didn't happen.
Definitely looks like the basis for Mk II, with new mechanics, better progression of difficulty and some kind of score.