Beleaguered Castle deals every card face-up in one deck and lets you build down regardless of suit, one card at a time. Hard game, 25% win rate.

Beleaguered Castle Solitaire is a tough game with dead-simple rules: every card is dealt face-up, you build down regardless of suit, and you move only one card at a time. It's often called "FreeCell without the cells," and it plays a bit like Baker's Dozen too. Single deck, hard difficulty, a 25% chance of winning, and your odds come down mostly to skill.
Other members of the castle family include Streets and Alleys Solitaire, Selective Castle, Stronghold, Citadel, Chessboard, and Bastion Solitaire, which adds a pair of storage cells to the same basic layout.
If you enjoy Beleaguered Castle, its nearest classic relative is FreeCell; the family resemblance is right there in the nickname.
If you run into anything odd or have an idea that would make the game better, please contact me.
Enjoy yourself!
4 foundation piles: Build up from Ace to King in the same suit. Each pile starts with an ace, dealt at the beginning of the game.
8 tableau piles: Build down regardless of suit. Only the top card of each pile is playable. Any available card can fill an open space. Each pile starts with 6 cards face-up.
There are four foundation piles.
Each foundation pile starts with an ace.
A card joins a foundation pile only if it's one rank higher than the pile's top card and the same suit, so the only card that can land on a jack of diamonds is the queen of diamonds.
The top card of any foundation pile can be moved back into play if another pile will take it.
Eight tableau piles hold six cards each, all dealt face-up.
A card joins a tableau pile only if it's one rank lower than the pile's top card, regardless of suit, so any six can land on any seven.
Any uncovered tableau card is free to move to the foundation or another tableau pile.
Any card can fill an empty tableau slot.
Only one card moves at a time.