in reply to
Challenge: Designing A Computer Opponent
Discussion on the CB led me to some ideas for you...
Do you use a dictionary of words that the computer opponent uses to find words to guess? If so, you could simply generate different dictionaries for different difficulty levels. There may even already be pre-computed dictionaries available online with words rated by how common/simple they are, and thus provide a convenient basis for categorization!
Also, the type of analysis required to solve the problem lends itself well to recursive solutions... perhaps build-in a (configurable) limit to how deep the analysis goes?
If all else fails, or isn't enough, I am partial to my earlier suggestion - make the computer make mistakes! Randomly inject bad data into the algorithm in the form of bad or mis-spelled dictionary entries, randomly delete previously-guessed entries, etc...
Update: While I don't have the time right now to come up with code, it looks like what's needed is some degree of intelligence for how to hamper a solving algorithm in a somewhat-consistient human-like fashion. My experience with programming for work points me towards a more straight-forward modeling approach with a pile of configurable-options that are tweaked until it 'feels' right, but my inner nerd wants something more like AI. I'll keep thinking about it, but I'd bet soup-to-nuts there's about 1000 monks here who could do this 10x faster and better than I :)