The unique thing about this Klondike inspired game is that empty columns can be filled with any SINGLE card but not a stack of cards. All three variations are free-to-play, no in-app purchases.
RUSH: You get 3 passes through the deck, 3, 2 then 1 card at-a-time.
1-CARD: one pass through the deck 1 card at a time.
3-CARD: unlimited passes through the deck 3 cards at a time.