Trigon is one of the cleanest experiments in solitaire. Take Klondike and change exactly one thing: instead of building down in alternating colours, build down in the same suit. Everything else — the seven-column staircase, the single turned card at the tip of each column, one card off the stock at a time, unlimited redeals, Kings only in the spaces — stays identical. That one change roughly halves the places every card can go, and it makes the game much harder than Klondike. Free in your browser, no sign-up.
Goal: build all four foundations from Ace to King by suit.
Suit building makes every host precious. A black 8 in Klondike welcomes two different red 7s; here the 8 of spades welcomes the 7 of spades and nothing else in the entire deck.
Trigon is registered in the PySol Fan Club collection as a Klondike variant, and its implementation is a single line: swap the alternating-colour tableau stack for a same-suit one that still requires a King in an empty column. Nothing else in the class exists. That makes it the most precise possible measurement of what Klondike's alternating-colour rule is worth, because it is the only variable that changes.
Same-suit building is a recurring idea across solitaire and it almost always makes a game markedly harder, which is why designers usually pay for it somewhere else — with free cells, with more columns, or with an open board. Trigon pays for it with nothing at all, and simply accepts the difficulty. This is the same trade the Forty Thieves family makes, and it is why that family has its reputation.
Its siblings in this catalogue show the other directions the same board can be pushed. Thumb and Pouch loosens the build instead of tightening it — any suit but the card's own — and opens the spaces to any card. Chinaman takes that same loose build and puts the King rule back. Saratoga keeps Klondike's rules exactly and reveals every card instead. Playing them in turn is a short course in what each individual rule does.
One honest note on difficulty. PySolFC rates Trigon balanced, but no published win rate for it that we can find carries a method or a sample size, so this page quotes none. What is structural rather than measured: suit building roughly halves the destinations available to every card, and nothing in the rules compensates for it, so expect to win considerably less often than at Klondike.
By one rule. The tableau builds down in the same suit instead of in alternating colours. The staircase deal, the single card turned from the stock, the unlimited redeals and the King-only spaces are all identical to Klondike.
Because it roughly halves where every card can go. In Klondike a black 8 accepts either red 7; in Trigon the 8 of spades accepts only the 7 of spades, so most cards you turn up have nowhere at all to land.
Yes, when they form a packed run descending by one in a single suit. The whole run travels together onto the next card up in that suit, or into an empty column if it is headed by a King.
Only a King, or a run headed by a King. This is Klondike's rule unchanged, so an empty column is worth nothing until you have a King you can actually reach.
As often as you like — redeals are unlimited. But when a full pass produces no legal move, another pass will not either, because nothing on the board has changed in the meantime.
More readily than in Klondike, yes. A card kept in the tableau only helps if the exact next card of its own suit appears, which is a long shot, so holding cards back costs you less often here.