Klondike's triangle grows to nine piles and two decks here, a notch harder than Gargantua, with a 20% win rate for patient planners.

Pantagruel Solitaire is a two-deck Klondike with nine tableau piles instead of the usual seven, dealt the same triangular way: one card on the first pile, two on the second, and so on up to nine. It's a notch tougher than Gargantua Solitaire but still fairly approachable. This one earns its difficult rating: nine tableau piles punish careless moves, and even careful planning only gets you a win about 20% of the time, with luck deciding the rest. It's played with two decks.
If you like this style, Double Klondike Solitaire is the closest relative worth trying next.
If you run into anything odd or have an idea that would make the game better, please contact me.
Enjoy!
8 foundation piles: Build up from ace to king in the same suit.
9 tableau piles: Build down by alternating color. A run of cards going down by alternating color can be moved as a group. Any card can fill an empty space. At the start of the game, the first pile gets one card, the second gets two, and so on up to the ninth pile with nine cards. The top card of each pile is dealt face-up.
Stock: Click to turn over one card to the waste pile. There are no redeals.
Waste: The top card can be played to the foundations or tableau.
There are eight foundation piles.
Any ace can be placed on an empty foundation pile.
A card can be added to a foundation pile only if it's one rank higher and the same suit as the pile's current top card, so the only card that fits on a six of diamonds is the seven of diamonds. A pile holds at most 13 cards.
The top card of any foundation can be moved back into play if another pile will take it.
Nine tableau piles: one card in the first pile, two in the second, three in the third, and so on up to nine in the last. The top card in each pile is dealt face-up, and the rest are dealt face-down.
A card can be added to a tableau pile only if it's one rank lower and the opposite color of the pile's current top card, so the only cards that fit on a jack of hearts are the ten of spades and ten of clubs.
Any tableau card that isn't covered by another card is free to move to the foundation or another tableau pile.
Any card can fill an empty tableau space.
A run of cards in alternating red-and-black order can be moved together from one tableau pile to another.
The waste pile holds the cards dealt from the stock; whatever's left makes up the stock.
Click the stock to deal one card at a time to the waste. You get a single pass through the stock, with no redeals.
The top card of the waste can be played to the tableau or foundation.