Simple, fun and challenging! Keep up the good work and especially with the simple, no-frills classic games. This kind of platform in the current era is the only way that the classic games will be preserved in cultural knowledge and passed on to future generations.
I dont think that "newer games", e.g., Candy Crush or Angry Birds", will exist or even be remembered in a generation; the classics stand a good chance. It will take companies like this one developing the apps for emerging platforms and technologies for that to happen.
CapKirk1963 about ▻ Solitaire