Ninja Avenger

From publisher blurb: Your friend Nada signed a piece of paper she shouldn't have, and now you could both be in big trouble. So the two of you travel into the twenty-first century to try to get the paper back and destroy it. But first you must face the deadliest robot ever created--the ninja cyborg. Should you use judo to stop the ninjaborg? Or can you defeat it with a Zen riddle that will tie up its logic systems?