It's all near-perfect... but why letters?
I suppose with letters you could argue it's slightly easier to remember them, but I think I prefer playing with pictures.
Everything else is basically perfect. The pink panther tune is an excellent one (as I'm sure you're aware) and fits the mood perfectly. It's nice how you've made it random, and the coding all seems to work perfectly. (Good job!)
Maybe you could make another installment and allow folk to choose between 5 different types of cards? You could have letters, numbers, different numbers of dots, solid colours or pictures...
The only real down-side to this game is the lack of originality.