Just a couple of thoughts.

To hamper the computer, presuming you have a good algorithm for guess():

- Have the computer select n words at random from its list. If none of these words fit the grill, it 'times out'.

- Add m misspelt words to the computer's list.

By adjusting m and n (down to zero and up to infinity, respectively, for 'expert' level), you can configure any number of levels.

Choice of dictionary:

- If the dictionary is too small, players will get fed up with the program refusing quite common words (including inflected forms, which seem to be allowed by the rules).

- If, on the other hand, it's too big*, there's a chance that it will too often choose extremely obscure words, again annoying the player.

Maybe use two wordlists, a fairly simple one from which the words to guess are selected, and a more comprehensive one to check for existence/spelling?

bahut, bahuts, bahuvrihi, bahuvrihis, baidarka, baidarkas, baigan, baigans, baignet...

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