Ask HN: Resources for gameplay design?

Does anybody know of articles or methodologies for designing the rules of games? My son has what I think is a pretty good idea for a battle card type game, but I know that playability of rule sets is a pretty complex thing. I think maybe we can design by analogy from things like Yu-Gi-Oh and Pokemon, but it would be even better if somebody had already put some thought into this and published the results.