Play: 21 browser games from the 561 Group that show you the odds
[Play](https://play.561.group/) is the 561 Group's games shelf: 21 titles, listed as playable in its catalog generated on 2026-10-04, from solitaire and Go to dice games that show you the exact probability of busting before you roll. The house style is honesty about numbers. Where a game involves chance, its practice-money versions display the computed odds, expected value or house edge on screen instead of hiding them, and they say that no real currency enters or leaves.
This is a short guide to what is on the shelf and what is distinctive about it. Availability can change: the catalog itself notes that page reachability is observed separately and "does not prove that a game works", so treat the list as the Group's report, not a guarantee.
What games are on Play?
The catalog sorts games into shelves. The ones worth a visit first:
| Shelf | Game | What it is |
|---|---|---|
| Card Table | Solitaire (solitaire.561.group) | Klondike, FreeCell, Spider in 1, 2 and 4 suits, Yukon, Forty Thieves, Golf, TriPeaks and Pyramid, all read from one declarative rules specification, with deterministic seeded deals and a solver-certified FreeCell generator |
| Card Table | Kelly's Wager (gambling-trainer.561.group) | A daily-seeded practice-bankroll trainer for expected value, variance and Kelly-criterion bet sizing; every offer is graded against the real Kelly optimum |
| Card Table | Pig, Yacht, Farkle, Chutes & Ladders, Fair Spin (parlor.561.group) | Parlor games that display the computed probabilities as you play |
| Puzzle Den | Crucible (crucible.561.group) | A daily-seeded settling puzzle where each move is a deterministic, replayable transformation of a reaction network and its measured obstruction cost |
| Puzzle Den | Stoke (stoke.561.group) | An incremental game where prestige is the dominant eigenvalue of your actual production matrix |
| Puzzle Den | TileSlots, Flickering Delve, You Are Conscious | A match-3 across square, hex and rhombille tilings; an idle roguelike where you write the standing-order program; an idle clicker built on Stoke's graph |
| Study | Weiqi (weiqi.561.group) | Go on 9x9 against four local bot tiers, plus lessons, tsumego with spaced repetition and replay |
| Study | Equivo | Seven lessons and thirty exercises on evidence readings and graph connectivity |
| Deep | Farstone, Ruinfold | A walkable 58-room New England harbor town; a daily roguelike where everyone descends the same keep |
The shelf also lists a 3D fantasy multiplayer game, two first-person shooters on the Group's own engine, and casino-style titles. Check each game's page for its rules and its economy before you play.
Which games teach probability?
Several, deliberately.
Pig is a hold-or-roll game, first to 100. "Every roll-or-hold decision shows the computed bust probability and expected value of rolling again — the teaching surface, not an afterthought." It is earn-only, practice scorekeeping only: no wagering, nothing staked.
Yacht has five dice, up to three rolls a turn and twelve categories. Every category shows its exact score if you commit now and its exact expected value if you reroll once more, recomputed live after every roll and every hold.
Farkle is dice-set scoring with hot dice and a real chance of busting the whole turn, again with computed bust probability and expected value on every decision.
Fair Spin is a three-reel practice slot "that inverts the genre": the computed return to player, the exact per-symbol hit odds and the expected loss per 100 spins sit permanently on the machine face, never behind a click, and a running session summary compares your actual spins against the published distribution. It uses a practice bankroll only.
Chutes & Ladders is the 100-square classic as a board graph. The catalog is candid that the "bots" are not opponents, since there is no strategy in this game: a bot is a die with a seating position. While the race runs, the exact probability distribution of how many more turns each player needs is computed live and shown.
Kelly's Wager goes furthest. It is a trainer for expected value, variance and Kelly-criterion sizing: each offer is graded against the real Kelly optimum, "adversarially-framed traps are labeled honestly by the numbers even when the pitch lies", and every spend is typed on screen as freely reversible, priced or terminal. Earn-only: no real currency ever enters or leaves.
Put together, they are a free, gentle way to build intuition about why a streak is not a strategy and why a house edge shows up over a hundred spins and not one.
What is the idea behind these games?
Three design rules recur in the catalog entries:
- Show the computation. Stoke's catalog entry says that every displayed number is tagged "computed-from-your-graph" or "designed-flavor", and that the game never blends the two without saying so. The odds-aware parlor games do the same for probabilities.
- Make state replayable. Many titles are daily-seeded (the same day gives the same puzzle to everyone) and declare a replay contract, so a result can be checked by replaying the recorded moves.
- Type the stakes. Where a game has an economy, each action is labeled on screen as freely reversible, priced or terminal, and the practice-money games say plainly that no real currency is involved. The Group does not present the casino-style titles as investments or as a source of income.
We note, in the Group's habit of reporting its own limits, that the catalog describes "reported playable" status, observed on 2026-10-04, and that several games note their own gaps in their catalog entries (for example, one game's removed cartridge layer is "to be re-wrapped when a real replay verifier export exists again"). A reachable page is not proof a game works well.
How does Play connect to the rest of the Group?
Play is one door among several. The others are Koios.News for reporting, the Turntide Islands community for climate adaptation (free to join; its site states plainly that it is "a conversation and a public record" today and carries no paid program, token or commercial obligation), and the machine-payable market for software buyers. The Group's own research on the mathematics behind some of these games, such as the bilattice death model in Ruinfold and the obstruction cost in Crucible, is at science.561.group, and the logic in question is the same four-valued kind that the market sells per call.
How do I start?
Open play.561.group. If you want one recommendation: try Pig, watch the bust probability on each decision, and see how often your gut disagrees with the arithmetic. Then try Kelly's Wager on a daily seed and compare each of your bets with the Kelly optimum it grades you against.