Sometimes I like to imagine what it was like when folks were first developing Uno. I think it might've gone something like the scene in
this week's cartoon. Making a game is full of surprises, which frequently revolve around players interpreting the rules in ways completely unimagined by the developer. The next step is to further define the rules - in some cases by coming up with an exception that covers the player's unorthodox response or rexamining the original rules and determining if the rule was really all that important to begin with. And so goes the process of game design. You design, test and apply the results of testing to your design. Lather, rinse, and repeat. Needless to say, this could go on forever (and sometimes does) but sooner or later you're going to have to say this is good enough to share with the rest of the world. When is that? If an overwhelming majority of your testers (say 80%) can get through it without any help (beyond that which ships with the product) then it's safe to say most of your users will as well.
BTW, I've changed the restrictions on posting in this blog. Anonymous posting is once more allowed. You still need to type in the verification code, I'm sick of spammers. But otherwise, feel free to share your thoughts, beg for advice, etc. I'm all ears!