Solitaire Progression
Starting with one unlocked solitaire (patience) game you must beat each game once to unlock the next of nine other games. All ten games are solitaire variations and are free-to-play once you have unlocked them.
No in-app purchases, just skill at playing solitaire.
Once unlocked a game remains unlocked so you can play it as often as you wish. This is a great way to get introduced to new types of solitaire (also called patience) games.