Add lobby and pack concept.

internal/game/packs.go

@@ -0,0 +1,35 @@
+package game
+
+// Card packs are the selectable sets of pets and food a game is played with.
+// Only the Turtle pack ships with real card data today; Golden and Unicorn are
+// declared here as infrastructure (shown but not yet playable) so the lobby,
+// views, and deck-building all have a single source of truth to grow into.
+
+// PackInfo describes one selectable pack. Playable gates whether a lobby may
+// choose it and start a game with it.
+type PackInfo struct {
+	ID       string `json:"id"`
+	Name     string `json:"name"`
+	Emoji    string `json:"emoji"`
+	Playable bool   `json:"playable"`
+}
+
+// DefaultPack is the pack a freshly created game starts on.
+const DefaultPack = "turtle"
+
+// Packs is the ordered catalog of packs shown in the lobby.
+var Packs = []PackInfo{
+	{ID: "turtle", Name: "Turtle Pack", Emoji: "🐢", Playable: true},
+	{ID: "golden", Name: "Golden Pack", Emoji: "🥇", Playable: false},
+	{ID: "unicorn", Name: "Unicorn Pack", Emoji: "🦄", Playable: false},
+}
+
+// packByID looks up a pack, returning false if the id is unknown.
+func packByID(id string) (PackInfo, bool) {
+	for _, p := range Packs {
+		if p.ID == id {
+			return p, true
+		}
+	}
+	return PackInfo{}, false
+}