How to Play

A single-deck patience game with four reserve piles and four foundations. Foundations build by suit only (no rank order) but each row filters through the row above: a card may only play if its rank already appears in every foundation higher.

Osmosis (also known as Treasure Trove) is a distinctive single-deck patience game dating to the mid-20th century, built around an unusual foundation-filtering rule that gives the game its name. Unlike standard patience foundations that build upward in rank, Osmosis foundations build by suit only (any rank order allowed), but with a strict cascade constraint: a card can only be played to a foundation if a card of the same rank already appears in the foundation row above it. This 'osmotic filtering' creates a cascading dependency where the first (top) foundation drives the entire game, and each lower foundation receives ranks only as the row above releases them. Four reserve piles of four cards each sit to the left of the foundations; only the top card of each reserve is face-up and playable, with cards beneath flipped only as the stacks are peeled. A stock of 35 cards is dealt three at a time to a waste pile, with unlimited redeals. Osmosis offers a moderate win rate (around 1 in 6 games) and rewards patient planning over speed.

Players

One player only; Osmosis is a solo patience game. It works with a physical deck on a table or on any of the major digital patience collections.

Card Deck

A standard 52-card deck; no jokers. No suit is preferred; the first foundation's suit is randomly determined by the first card dealt from stock. Cards within a foundation do not need to be in ascending or descending rank order; any rank order within a single suit is valid.

Objective

Move all 52 cards to the four foundations, each built up by suit only with no rank-order requirement, subject to the osmosis filter rule: a card may only be played to a foundation below the top row if a card of the same rank has already been placed in every foundation above it.

Setup and Deal

1. Shuffle the 52-card deck.
2. Deal 4 reserve piles of 4 cards each in a vertical column on the left side of the play area. Only the top card of each pile is turned face-up; the three beneath it are face-down.
3. Turn over the next card from the stock and place it to the right of the topmost reserve pile as the first foundation. The suit of this card becomes the suit of the first foundation.
4. The remaining 35 cards form the stock, placed face-down to the right of the reserve.
5. Designate a space below the stock for the waste pile, where stock deals will be stacked face-up three at a time.
6. The three foundations for the other suits will be added in successive rows below the first foundation as they are started.

Gameplay

1. First foundation (top row): Plays any card of its suit in any rank order. Example: if the first foundation is the Spades foundation and started with , you can later add , , , etc. in any order.7♠A♠K♠3♠
2. Second foundation (row 2): Started by a card of any other suit, placed below and aligned with the first foundation. This foundation may only accept cards whose rank already appears in the first foundation. If the Spades foundation contains 7-3-K, then the Hearts foundation can only accept 7s, 3s, and Ks of Hearts (any order).7♥3♥K♥
3. Third foundation (row 3): Similarly constrained: accepts a card only if its rank appears in both the first and second foundations above it.
4. Fourth foundation (row 4): Accepts a card only if its rank appears in all three foundations above.
5. Starting a new foundation (rows 2, 3, 4): A new foundation is started only when a card matches the starting rank of the first foundation. Example: if the first foundation started with 7♠, then each of the lower three foundations begins with the 7 of its respective suit. So to start the Hearts foundation (row 2), you must play the 7♥.7♠7♥
6. Reserve play: Only the top card of each of the four reserve piles is playable at any time. When a top card is played to a foundation, the card beneath it is flipped face-up and becomes the new top.
7. Stock: When no useful moves remain, deal 3 cards from the stock face-up to the waste pile, landing as a packet. Only the top card of the waste pile is playable at any time. Continue playing face-up cards until the stock is exhausted.
8. Redeal: When the stock is exhausted, collect the waste pile (do not shuffle) and flip it face-down as the new stock. Unlimited redeals are permitted, but you must make progress between redeals; if you complete a full redeal pass without playing any card, the game is stalled.

Scoring

• Win condition: All 52 cards successfully moved to the four foundations.
• Partial score: When the game stalls, count the total number of cards on foundations. Useful for tracking improvement across attempts.
• Estimated win rate: Approximately 1 in 6 games with optimal play. Skilled players can push the rate higher by careful stock-waste management.

Winning

You win when all 52 cards are on the four foundations. There is no time limit; the game ends either in a win or in a stall where no legal moves remain and a full redeal produces no progress. The game is considered well-played if you reach at least 40 cards on foundations even in a losing attempt.

Common Variations

• Peek (Open Osmosis): All reserve cards are dealt face-up from the start, letting you plan around the complete reserve pile contents. Raises win rate to roughly 1 in 3.
• Single-card deal: Deal one card at a time from the stock instead of three to the waste pile. Dramatically increases win rate to roughly 1 in 3 and makes the game feel more deterministic.
• Limited redeals: Classic strict rules limit to 3 passes through the stock rather than unlimited. Significantly harder.
• Treasure Trove: The original name for the game as published in early 20th-century patience compendia. Rules identical to modern Osmosis.
• Bridesmaids: A rare closely related variant that sometimes appears in solitaire apps; nearly identical but with a one-deal rule.

Tips and Strategy

• Build the first foundation aggressively: The entire cascade depends on the first foundation. Every new rank added to the top row unlocks play on all three rows below. Prioritise playing first-foundation-suit cards above all else.
• Track ranks already in the first foundation: Keep a mental note of which ranks have entered the top row. You only need the first foundation to contain all 13 ranks for every other foundation to have full freedom, at which point the cascade is solved.
• Hold off on starting new foundations: A new foundation below the top row is only started when its matching starter rank appears. You can choose to delay starting row 2 (if the starter card is on a reserve pile top) in order to wait for favourable top-row progress. However, delay is a bet against the stock.
• Do not peel reserves randomly: Each reserve pile hides 3 face-down cards. Playing a top-reserve card to build a foundation is always positive, but beware of playing reserve cards to the waste or into non-critical foundations when they could later be useful.
• Use redeals patiently: Redeals are unlimited, but each pass exposes every card in different offsets. Plan a full circuit: think through which waste-pile cards will become playable in the current configuration and which will not.

Glossary

• Reserve pile: One of four 4-card face-down stacks with only the top card face-up; source of early cards.
• Foundation: One of four piles, each accepting only its own suit. Top-row foundation has no rank filter; lower foundations filter by the osmosis rule.
• Osmosis filter / cascade rule: A card may only enter a foundation if its rank already appears in every foundation above it.
• Stock: The 35 undealt cards remaining after setup.
• Waste pile: The face-up pile where stock cards are deposited in packets of 3 (or 1 in the single-deal variant).
• Redeal: Flipping the waste pile back into the stock when the stock exhausts. Unlimited in the standard rules.
• Starter rank: The rank of the first card dealt to the top foundation; every foundation below the first must start with this rank.