Every foundation locks to one shared rank, and ten tableaus build same-suit runs that wrap King back to Ace. A tighter, trickier take on Chessboard.

Castle's End Solitaire is a slightly modified version of Chessboard Solitaire, reworked with a two-card reserve. Any card can start an empty foundation pile, but once one pile has been started, every other empty pile must begin with that same rank. On the ten tableau piles, you build a same-suit run up or down, wrapping from King back around to Ace.
Where Castle's End tightens the screws with locked foundation ranks, FreeCell opens things back up with room to maneuver.
If you run into anything odd or have an idea that would make the game better, please contact me.
Enjoy yourself!
There are four foundation piles.
Any card may start an empty foundation pile, but once one pile has been started, every other empty pile must begin with that same rank.
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 J of clubs is a Q of clubs.
The top card of each foundation can be moved back into play if another pile will accept it.
There are two reserves, each with one card at first. Nothing can be moved into the reserves. Each reserve's top card can be played to the tableau or the foundation.
There are ten tableau piles of five cards each, all dealt face-up.
A card can be added to a tableau pile only if it's one rank higher or one rank lower and the same suit as the pile's current top card, so the cards that fit on the Q of diamonds are the J and K of diamonds. You can also play the tableau's highest card straight onto its matching foundation pile.
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 card can fill an empty slot in the tableau.
Only one card can be moved at a time, though super moves let you shift a whole sequence at once when there are enough empty tableau piles to fake the same result one card at a time.