Space Poker Rules

Early Alpha Release

Space Poker is included in Alpha 2 as an early release. On-chain Chialisp, rules, and UI may change before general availability. The rules below match the current implementation in the chia-gaming repository (clsp/games/spacepoker/).

Objective

Space Poker is a two-player, suitless Hold'em-style game on a single shared board. Each player gets two hole cards; five community cards are dealt (flop, turn, river). Players bet over four streets, then the best five-card hand wins the pot. Each player also has a boost flag (+ or −) that can break ties within the same hand class.

There is one hand per game in the channel, not two parallel boards.

Setup

Stakes

When starting Space Poker in the player app, you set:

• Unit size: mojos per betting unit (bet_unit on-chain).
• Stack size: number of units each player brings (default 10 in the UI).

Total locked stake for the hand is 2 × unit size × stack size mojos (AMOUNT in the on-chain validators). The minimum increment used in the protocol is bet_unit = total per-player stake ÷ 10. The UI slider raises in whole units; the chain accepts any valid non-negative raise in mojos up to each player's remaining stack.

Cards and boost

• Hole cards and community cards are ranks 2–A only (T=10, J=11, Q=12, K=13, A=14). There are no suits.
• Each player receives two hole cards, drawn deterministically from commit entropy (see derive_all_cards in chia-gaming).
• Each player gets one boost for the hand: + with probability ⅓, otherwise − (derived from hashed commit material, not from individual cards).
• Community cards are shared: flop (3), then turn (1), then river (1), revealed in that order as streets complete.

Opening the hand

1. Both players post hash-chain commits (commitA, commitB).
2. commitB posts the first unit into the pot (half_pot starts at one bet_unit).
3. Betting begins at pre-flop (N = 4 in the validator state).

Hand Rankings

From lowest to highest:

1. High Card: No pair or better
2. Pair: Two cards of the same rank
3. Two Pair: Two different pairs
4. Set (Three of a Kind): Three cards of the same rank
5. Full House: Three of a kind plus a pair
6. Straight: Five consecutive ranks (high card of the straight breaks ties within the class)
7. Four of a Kind: Four cards of the same rank
8. Five of a Kind: Five cards of the same rank

Important differences from traditional poker:

• No flushes: ranks only; suits do not exist.
• Five of a kind is the highest hand.
• No ace-low wheel: A-2-3-4-5 is not a straight (only five consecutive ranks where the top card is exactly four above the bottom, e.g. 6-7-8-9-10).
• Straight beats full house: in this suitless deck, straights are rarer than full houses (see space_hand_eval.clinc).

Tiebreakers

Hands are compared as structured values (hand counts… boost rank kickers…) using lexicographic ordering (deep_compare in Chialisp):

1. Hand class: e.g. full house beats set; straight beats full house.
2. Boost: with the same class, + beats − (boost does not upgrade you to a higher class; a boosted set still loses to an unboosted full house).
3. Kickers: remaining rank fields in the hand tuple, highest first.

At showdown each side automatically selects the best five cards from their seven (two hole + five board) via space_hand_calc; players do not manually pick cards in normal play.

Gameplay

Streets

Four betting rounds map to standard street names:

Validator N	Street	Board state
4	Pre-flop	Hole cards only
3	Flop	Three community cards
2	Turn	Fourth community card
1	River	Fifth community card; then showdown

Pre-flop coin toss

On the first street only (N = 4), a coin toss (from compared hash-chain images) decides who opens betting:

• Opener: sends an open move: optional raise amount (0 = check).
• Non-opener: may pong (defer opening; roles swap, toss flips) once, then the other player opens.

This is enforced on-chain in begin_round.clsp so the opener cannot ignore an unfavorable toss by checking.

Turn Structure

Players alternate on each street. The opener acts first with check or raise; the other player responds with call or raise in mid_round. A call ends the street (or goes to showdown on the river). See Pre-flop coin toss above when N = 4.

Actions per street

Phase	Your turn options (UI)	On-chain meaning
begin_round	Check or Raise	Open with 0 or more mojos added to half_pot
mid_round	Call or Raise	Match the current raise, or raise again
end	(automatic reveal)	Best-five selection and payout

• Check: only when you are the opener on a street (begin_round).
• Call: matches the last raise and ends the street (or proceeds to showdown on the river).
• Raise: increases the wager; opponent must call or re-raise in mid_round.
• Fold (UI only): forfeits the current hand through the protocol timeout path (acceptTimeout in the player app). This is not a separate on-chain fold opcode and is not a network or connection timeout. Use only when you intend to abandon the hand outside normal call/raise flow.

After a call on streets 4–2, the next street deals the next community card(s). After a call on the river (N = 1), play moves to showdown.

Showdown

• Both players' best five-card hands are computed from seven cards (hole + board).
• The mover reveals with a preimage and five-card bitfield; the waiter must match with their own best five (end.clsp).
• The UI shows win/loss/split, pot result, evaluated hand names, and hole cards when the protocol exposes them in readables ("call" on the river or "end").
• There is no “must show only if you lose” rule in the validators; display follows what the handlers emit.

All-In

Stack limits are enforced by validator state: total committed chips per player cannot exceed half of AMOUNT. When a player cannot raise further, they call or check with what remains; there is no separate “all-in” opcode; the UI tracks stack and pot from half_pot and raise amounts.

Game Flow

1. Proposal: Agree on unit size and stack size; both fund the game coin.
2. Commits: Hash-chain commits; hole cards and boost are fixed from entropy.
3. Pre-flop: Coin toss (if needed), then check/raise and call/raise until the street closes.
4. Flop → Turn → River: Each street: opener check/raises, opponent calls or raises, then the next board cards appear.
5. Showdown: River call or final reveal; pot split by hand comparison.
6. Next hand or session end: Start another hand from the lobby if balances allow, or shut down the channel (clean shutdown returns funds in Alpha 2 builds).

Session end

A session may end because:

• Players finish and choose not to continue
• Insufficient balance for the next stake
• Clean shutdown or channel close on-chain
• A player uses Fold (protocol timeout via acceptTimeout) in the UI to abandon the current hand

For installation, WalletConnect, and testing steps, see the Users Guide and Developers Guide.