gyla

README

Gyla

A card game engine for a traditional trick-taking card game.

Game Rules

Players & Teams

• 4 players split into 2 teams: Player 1 + Player 3 = Team 1, Player 2 + Player 4 = Team 2.
• Players sit in a circle: P1 → P2 → P3 → P4 → P1 (left opponent order).
• Players can be human or AI.

Cards

• 9 ranks: 6, 7, 8, 9, 10, Jack, Queen, King, Ace.
• 4 suits: Clubs, Spades, Hearts, Diamonds.
• 36 cards total, 9 dealt to each player.

Trumps

There are two kinds of trumps:

1. Default trumps — all 7s and all Jacks are always trumps regardless of the chosen suit (8 cards total).
2. Suit trumps — when a player chooses a trump suit, all remaining cards of that suit also become trumps.

Card Hierarchy

Trump cards (highest to lowest):

#	Card
1	6 of trump suit (highest card in the game)
2	7 of Clubs
3	7 of Spades
4	7 of Hearts
5	7 of Diamonds
6	Jack of Clubs
7	Jack of Spades
8	Jack of Hearts
9	Jack of Diamonds
10	Ace of trump suit
11	King of trump suit
12	Queen of trump suit
13	10 of trump suit
14	9 of trump suit
15	8 of trump suit

Non-trump cards (within their suit, highest to lowest):

Ace → King → Queen → 10 → 9 → 8 → 6

Round Lifecycle

1. Cards are dealt (9 per player). If any player receives all four 7s or all four 6s, the hand is re-dealt.
2. The starter (trumper) assigns a trump suit.
3. 9 tricks are played (4 cards each, using all 36 cards).

Determining the Starter

• First round: The player holding the 9 of Diamonds starts.
• Subsequent rounds:
  • If the team that assigned trump won the round, the same player assigns trump again.
  • If the team that assigned trump lost, the left opponent of the previous starter becomes the new starter.

Trick Rules

1. The trick starter plays any card.
2. Other players must follow suit:
   • If the lead card is a trump → you must play a trump if you have one.
   • If the lead card is a non-trump suit → you must play a card of the same suit (non-trump only). If you don't have any, you can play anything.
3. Trick winner:
   • If any trumps were played → the highest trump wins.
   • If no trumps were played → the highest card of the leading suit wins.
4. The trick winner starts the next trick.

Scoring

The team that wins more tricks (5+ out of 9) wins the round. Draws are impossible.

Points awarded to the winning team per round:

Tricks Won	Points
All 9	24
8 out of 9	18
5 to 7	6

Bonus: If the winning team is not the team that assigned trump, they receive an additional +6 points.

Game end: The game ends when a team reaches 60 points.

Usage

package main

import "github.com/vetalpaprotsky/gyla/game"

func main() {
	g := game.NewGame(
		"Alice", "Bob", "Charlie", "Diana",
		"Team Alpha", "Team Beta",
		false, true, false, true, // players 2 and 4 are AI
	)

	events, err := g.Start()
	// handle events...

	events, err = g.Apply(game.Action{
		Name:   game.AssignTrumpAction,
		Player: game.Player1,
		Suit:   game.HeartsSuit,
	})
	// handle events...

	events, err = g.Apply(game.Action{
		Name:   game.PlayCardAction,
		Player: game.Player1,
		Rank:   game.AceRank,
		Suit:   game.HeartsSuit,
	})
	// handle events...
}

Running Tests

cd game && go test -v ./...