I have edited two things:
1) Buddha-nature is hyphenated and capitalized, per the original rules at wunderland.com. (See Buddha-nature for additional Discussion and a link to those rules.)
2) The Master in Ikkozendo may adjust one or both of the two koans, if needed to disprove a guess. This often occurs when the secret rule is color-based.
David Artman (creator of Ikkozendo)