I was gonna recommend the same one. I wanna add that Hempuli (Baba is You, Noita) also made a solitaire collection inspired by Zachtronics. It's just 3 bucks on his itchio and it's something I play while I have my coffee.
The Solitaire Mystery is also the name of a very interesting novel that explores all kinds of permutations of the cards, suits, etc, etc, by Jostein Gaarder, author of Sophie's World.
Zachtronics Solitaire Collection inspired me to begin experimenting with Solitaire variants, and hopefully Balatro's well-deserved success will stoke people's curiosity in similar titles.
For now, my web prototype lets you choose the numbers of suits, colors, ranks, columns, and multiples of cards drawn from the deck. It's a start. I invite HN to explore the Klondike Extended Universe:
I LOVE that you let the player tweak those variables in the mechanics. Many of us want to be able to relax with a nice comfy game for half an hour, and "comfy" means setting the difficulty just right.
My partner used to relax with Flipflop Solitaire[1], which lets you choose how many suits there are in the deck. These days they play lots of Balatro with the checkered deck[2].
Thirding this recommendation, Fortune's Favor solitaire and Shenzen solitaire from this collection are some of my favorite variants ever. Either of them would be worth the price of admission alone.
I absolutely love the Zachtronics solitaires. I play at least one a day on my phone. That said, I wish they were slightly better designed for phones, since the text/images and touch targets can be a little small. It's too bad Zachtronics is no more -- it'd be nice if they were able to do some UI updates.
https://hempuli.itch.io/a-solitaire-mystery
Funny enough it has a "Royal Flush Solitaire" where you make poker hands and your goal is to reach 240 points.
Binary Solitaire and Transformation are my favorites.