Clear the tableau by matching four of a kind among the 10s and face cards, or any cards nine and under that add up to fifteen. Easy, single deck, and a 95% win rate.

Fifteens Solitaire is a simple matching game: clear cards off the tableau by putting together four 10s, four Jacks, four Queens, or four Kings as a set, or by matching any cards ranked 9 or below whose values add up to 15. Matching sums this simple is why the game rates easy: about 95% of deals can be won. It's a single deck, and chance does most of the deciding here.
Other solitaire games comparable to this one include Fifteens Suit, Block Ten, Elevens, Pyramid Solitaire, Fourteen Out Solitaire, and Eighteens Solitaire.
If you run into anything odd or have an idea that would make the game better, please contact me.
Enjoy playing!
4 foundation piles: Discard piles for matched sets and pairs. There's no building here and no limit to how many cards stack up.
16 tableau piles: Each pile is dealt one card face-up at the start. Match four 10s, four Jacks, four Queens, or four Kings together, or any combination of cards ranked 9 or below that adds up to 15, and send them to a foundation pile. Empty tableau spots are refilled at once from the stock; once it runs out, they stay empty.
Stock: Made up of the leftover cards after the deal. Cards can't be dealt from it by hand; it refills empty tableau spots automatically until it runs out.
There are four foundation piles. Matched sets and pairs are stacked here as they're cleared from the tableau.
There are sixteen tableau piles of one card each. Every card is dealt face-up.
On the tableau, no building is allowed; cards are only ever matched and removed.
The cards on the tableau are playable, matched either as four of a kind among the 10s, Jacks, Queens, and Kings or as any combination of cards ranked 9 or below that adds up to 15.
An empty tableau spot is refilled at once with the top card of the stock. Once the stock runs out, empty spots stay empty.
The stock is made up of leftover cards.
Cards cannot be withdrawn from the stock manually. Instead, it refills each empty tableau spot automatically with its top card until it runs out.