Deal three decks into a nine-pile checkerboard, then chase a coin-flip finish: Triple Interchange sits at medium difficulty with a 50% win rate.

Triple Interchange Solitaire triples the deck of Interchange Solitaire: three decks, twelve foundation piles, and nine tableau piles of nine cards each, dealt in a face-up, face-down checkerboard. It's medium difficulty with a 50% chance of winning, played with three decks, and your odds come down to skill and luck alike.
Comparable games include Quadruple Interchange Solitaire, which adds a fourth deck and even more piles.
When you want something quieter than a checkerboard of nine piles nine cards deep, the classic Solitaire is right there.
If you run into anything odd or have an idea that would make the game better, please contact me.
Enjoy!
12 foundation piles: Build up from Ace to King in the same suit.
9 tableau piles: Build down in suit. A same-suit run can move down together as a group. Any single card, or a same-suit run, can fill an empty pile. Each pile starts with 9 cards, alternating face-up and face-down.
Stock: Click to flip one card at a time to the waste. Redeals are unlimited.
Waste: Top card is always available for play on the foundations or tableau.
There are twelve 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 10 of hearts is a J of hearts. No pile can hold more than 13 cards.
The top card of each foundation can be moved back into play if another pile will accept it.
Nine tableau piles of nine cards each, dealt in a checkerboard: even-numbered cards face-down, odd-numbered cards face-up.
A card can be added to a tableau pile only if it's one rank lower and the same suit as the pile's current top card, so the only card that fits on an 8 of clubs is a 7 of clubs.
Cards on the tableau that are not covered by another card are free to be played onto the foundation or any other tableau pile.
Any single card, or a same-suit run of cards, can fill an empty tableau pile.
If every card in a run shares the same suit, the whole sequence can be moved from one tableau pile to another.
There is one waste pile and the remaining cards make up the stock.
When you click the stock, one card is dealt to the waste. You can go through the stock as many times as you like.
The top card of the waste can be played to the tableau or foundation.