Add lobby and pack concept.

internal/game/cards.go

@@ -482,12 +482,23 @@ func (g *Game) newCardID() string {
 	return fmt.Sprintf("c%d", g.NextCardID)
 }
 
-// buildShopDecks creates all six tier decks (unshuffled).
+// packTiers returns the pet and food templates for a pack, tier by tier. Only
+// the Turtle pack has real data today; the other (not-yet-playable) packs fall
+// back to it so this is the single seam future packs plug their cards into.
+func packTiers(pack string) (*[MaxRounds][]petTemplate, *[MaxRounds][]foodTemplate) {
+	switch pack {
+	default: // turtle (and the placeholder packs, until they ship)
+		return &petTiers, &foodTiers
+	}
+}
+
+// buildShopDecks creates all six tier decks (unshuffled) for the game's pack.
 func (g *Game) buildShopDecks() {
+	pets, foods := packTiers(g.Pack)
 	g.ShopDecks = make([][]Card, MaxRounds)
-	for tierIdx := range petTiers {
+	for tierIdx := range pets {
 		var deck []Card
-		for _, t := range petTiers[tierIdx] {
+		for _, t := range pets[tierIdx] {
 			for _, suit := range t.Suits {
 				deck = append(deck, Card{
 					ID:         g.newCardID(),
@@ -501,7 +512,7 @@ func (g *Game) buildShopDecks() {
 				})
 			}
 		}
-		for _, f := range foodTiers[tierIdx] {
+		for _, f := range foods[tierIdx] {
 			for range f.Copies {
 				deck = append(deck, Card{
 					ID:         g.newCardID(),