golfgame/server/RULES.md

6-Card Golf Rules

This document defines the canonical rules implemented in this game engine, based on standard 6-Card Golf rules from Pagat.com and Bicycle Cards.

Overview

Golf is a card game where players try to achieve the lowest score over multiple rounds ("holes"). The name comes from golf scoring - lower is better.

Players & Equipment

• Players: 2-6 players
• Deck: Standard 52-card deck (optionally with 2 Jokers)
• Multiple decks: For 5+ players, use 2 decks

Setup

1. Dealer shuffles and deals 6 cards face-down to each player
2. Players arrange cards in a 2 row × 3 column grid:

   [0] [1] [2]   ← Top row
   [3] [4] [5]   ← Bottom row
   

3. Remaining cards form the draw pile (face-down)
4. Top card of draw pile is flipped to start the discard pile
5. Each player flips 2 of their cards face-up (standard rules)

Card Values

Card	Points
Ace	1
2	-2 (negative!)
3-10	Face value
Jack	10
Queen	10
King	0
Joker	-2

Column Pairing

Critical rule: If both cards in a column have the same rank, that column scores 0 points regardless of the individual card values.

Example:

[K] [5] [7]    K-K pair = 0
[K] [3] [9]    5+3 = 8, 7+9 = 16
               Total: 0 + 8 + 16 = 24

Note: Paired 2s score 0 (not -4). The pair cancels out, it doesn't double the negative.

Turn Structure

On your turn:

1. Draw Phase

Choose ONE:

• Draw the top card from the draw pile (face-down deck)
• Take the top card from the discard pile (face-up)

2. Play Phase

If you drew from the DECK:

• Swap: Replace any card in your grid (old card goes to discard face-up)
• Discard: Put the drawn card on the discard pile and flip one face-down card

If you took from the DISCARD PILE:

• You MUST swap - you cannot re-discard the same card
• Replace any card in your grid (old card goes to discard)

Important Rules

• Swapped cards are always placed face-up
• You cannot look at a face-down card before deciding to replace it
• When swapping a face-down card, reveal it only as it goes to discard

Round End

Triggering the Final Turn

When any player has all 6 cards face-up, the round enters "final turn" phase.

Final Turn Phase

• Each other player gets exactly one more turn
• The player who triggered final turn does NOT get another turn
• After all players have had their final turn, the round ends

Scoring

1. All remaining face-down cards are revealed
2. Calculate each player's score (with column pairing)
3. Add round score to total score

Winning

• Standard game: 9 rounds ("9 holes")
• Player with the lowest total score wins
• Optionally play 18 rounds for a longer game

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House Rules (Optional)

Our implementation supports these optional rule variations:

Standard Options

Option	Description	Default
initial_flips	Cards revealed at start (0, 1, or 2)	2
flip_on_discard	Must flip a card after discarding from deck	Off
knock_penalty	+10 if you go out but don't have lowest score	Off
use_jokers	Add Jokers to deck (-2 points each)	Off

Point Modifiers

Option	Effect
lucky_swing	Single Joker worth -5 (instead of two -2 Jokers)
super_kings	Kings worth -2 (instead of 0)
ten_penny	10s worth 1 (instead of 10)

Bonuses & Penalties

Option	Effect
knock_bonus	First to reveal all cards gets -5 bonus
underdog_bonus	Lowest scorer each round gets -3
tied_shame	Tying another player's score = +5 penalty to both
blackjack	Exact score of 21 becomes 0

Special Rules

Option	Effect
eagle_eye	Jokers worth +2 unpaired, -4 paired (spot the pair!)

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Game Theory Notes

Expected Turn Count

With standard rules (2 initial flips):

• Start: 2 face-up, 4 face-down
• Each turn reveals 1 card (swap or discard+flip)
• Minimum turns to go out: 4
• Typical range: 4-8 turns per player per round

Strategic Considerations

Good Cards (keep these)

• Jokers (-2 or -5): Best cards in the game
• 2s (-2): Second best, but don't pair them!
• Kings (0): Safe, good for pairing
• Aces (1): Low risk

Bad Cards (replace these)

• 10, J, Q (10 points): Worst cards
• 8, 9 (8-9 points): High priority to replace

Pairing Strategy

• Pairing is powerful - column score goes to 0
• Don't pair negative cards - you lose the negative benefit
• Target pairs with mid-value cards (3-7) for maximum gain

When to Go Out

• Go out with score ≤ 10 when confident you're lowest
• Consider opponent visible cards before going out early
• With knock_penalty, be careful - +10 hurts if you're wrong

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Test Coverage

The game engine has comprehensive test coverage in test_game.py:

• Card Values: All 13 ranks verified
• Column Pairing: Matching, non-matching, negative card edge cases
• House Rules: All scoring modifiers tested
• Draw/Discard: Deck draws, discard draws, must-swap rule
• Turn Flow: Turn advancement, wrap-around, player validation
• Round End: Final turn triggering, one-more-turn logic
• Multi-Round: Score accumulation, hand reset

Run tests with:

pytest test_game.py -v