I'm a big fan of vocabulary games like Scrabble and Words With Friends. This game adds a new way to play that formula that's less involved and solo. I could see this game being very successful as a mobile app. Imagine you're sitting on a train or waiting for someone in your car and you want to play something to stimulate your brain. This would be perfect. Consider adding an exp/level up system for winning with unlockables such as "Lock two letters in the right place," "give me a definition of the word," "What does it start with?" etc. This has potential!