You did a great job on designing the cribbage game. I've really enjoyed playing it. If you don't like the undo button, would you consider adding another button, such as an "add cards to crib" button? Maybe I'm not as coordinated at most, but at least once during a game I select the wrong card to put in the crib. It may be because I'm used to the way video poker works; you select the cards you want to keep, not the ones you want to throw away. I find myself trying to select 4 cards, and end up throwing the first 2 cards I select in the crib. The button could be similar to the buttons you have to select when you're counting: you select the cards, then have to hit pair, run, flush or whatever. For those that don't want to select another button (I'm usually all for making things as simple as possible), this could always be an option you could turn on or off. I like having less buttons, but I find that the older I get I make mistakes when selecting cards with a mouse, something that I wouldn't do if I were playing the game with actual playing cards.
Once again, thanks for all the hard work - it's a great game.