this clarifies a bunch of sections and seems slightly faster
target_word (which would be randomly selected from the input every
time) is replaced with seed_words, a shuffled list from the input.
this is to eliminate accidental reuse of the target word, which
would result in chains like X X X X X X X X X X X X X because
it'd keep targeting X
the rest of this is mostly just debug cleanup, though to simplify
the backwards code it only tries to find one target word
Brian S. Stephan
390e925360