Implement card pack system with gacha mechanics

Add card packs that can be opened via right-click Use menu to receive
random cards based on weighted slot configurations. Packs support
customizable rarity-based or card-specific drop rates.

Key features:
- CardPack/PackSlot data classes with weighted random selection
- PackParser for user-defined pack configurations
- PackUsageBehavior extending game's UsageBehavior system
- Runtime data lookup to handle Unity serialization limitations
- Pack consumption after opening with stack support
- Auto-generated default packs per card set

Technical notes:
- UsageUtilities registration for context menu integration
- All non-serializable fields (Dictionary, List<PackSlot>) looked up
  at runtime from ModBehaviour to survive Unity instantiation
- F9 debug spawn now uses InstantiateSync for proper item copies

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

TradingCardMod.csproj

@@ -50,6 +50,9 @@
         <Reference Include="UnityEngine.InputLegacyModule">
             <HintPath>$(DuckovPath)$(SubPath)UnityEngine.InputLegacyModule.dll</HintPath>
         </Reference>
+        <Reference Include="UniTask">
+            <HintPath>$(DuckovPath)$(SubPath)UniTask.dll</HintPath>
+        </Reference>
     </ItemGroup>
 
     <ItemGroup>

src/CardPack.cs

@@ -0,0 +1,155 @@
+using System.Collections.Generic;
+
+namespace TradingCardMod
+{
+    /// <summary>
+    /// Represents a card pack that can be opened to receive random cards.
+    /// </summary>
+    public class CardPack
+    {
+        /// <summary>
+        /// Display name of the pack.
+        /// </summary>
+        public string PackName { get; set; } = string.Empty;
+
+        /// <summary>
+        /// The card set this pack draws from.
+        /// </summary>
+        public string SetName { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Path to the pack's icon image.
+        /// </summary>
+        public string ImagePath { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Filename of the pack image (before full path is set).
+        /// </summary>
+        public string ImageFile { get; set; } = string.Empty;
+
+        /// <summary>
+        /// In-game currency value of the pack.
+        /// </summary>
+        public int Value { get; set; }
+
+        /// <summary>
+        /// Weight for appearing in loot (0 = not lootable).
+        /// </summary>
+        public float Weight { get; set; } = 0.1f;
+
+        /// <summary>
+        /// The slots in this pack, each with their own drop weights.
+        /// </summary>
+        public List<PackSlot> Slots { get; set; } = new List<PackSlot>();
+
+        /// <summary>
+        /// Whether this is an auto-generated default pack.
+        /// </summary>
+        public bool IsDefault { get; set; }
+
+        /// <summary>
+        /// Generates a unique TypeID for this pack.
+        /// Uses hash of set name + pack name for uniqueness.
+        /// </summary>
+        public int GenerateTypeID()
+        {
+            // Start from 300000 range for packs (cards are 100000+, storage is 200000+)
+            string uniqueKey = $"CardPack_{SetName}_{PackName}";
+            return 300000 + System.Math.Abs(uniqueKey.GetHashCode() % 100000);
+        }
+    }
+
+    /// <summary>
+    /// Represents a single slot in a card pack with drop weights.
+    /// Each slot can use either rarity-based or card-specific weights.
+    /// </summary>
+    public class PackSlot
+    {
+        /// <summary>
+        /// Whether this slot uses rarity-based weights (true) or specific card weights (false).
+        /// </summary>
+        public bool UseRarityWeights { get; set; } = true;
+
+        /// <summary>
+        /// Rarity-based weights. Key = rarity string (e.g., "Common"), Value = weight.
+        /// Used when UseRarityWeights is true.
+        /// </summary>
+        public Dictionary<string, float> RarityWeights { get; set; } = new Dictionary<string, float>();
+
+        /// <summary>
+        /// Specific card weights. Key = card name, Value = weight.
+        /// Used when UseRarityWeights is false.
+        /// </summary>
+        public Dictionary<string, float> CardWeights { get; set; } = new Dictionary<string, float>();
+    }
+
+    /// <summary>
+    /// Default slot configurations for auto-generated packs.
+    /// </summary>
+    public static class DefaultPackSlots
+    {
+        /// <summary>
+        /// Slot 1: Favors common cards.
+        /// </summary>
+        public static PackSlot CommonSlot => new PackSlot
+        {
+            UseRarityWeights = true,
+            RarityWeights = new Dictionary<string, float>
+            {
+                { "Common", 100f },
+                { "Uncommon", 30f },
+                { "Rare", 5f },
+                { "Very Rare", 1f },
+                { "Ultra Rare", 0f },
+                { "Legendary", 0f }
+            }
+        };
+
+        /// <summary>
+        /// Slot 2: Balanced towards uncommon.
+        /// </summary>
+        public static PackSlot UncommonSlot => new PackSlot
+        {
+            UseRarityWeights = true,
+            RarityWeights = new Dictionary<string, float>
+            {
+                { "Common", 60f },
+                { "Uncommon", 80f },
+                { "Rare", 20f },
+                { "Very Rare", 5f },
+                { "Ultra Rare", 1f },
+                { "Legendary", 1f }
+            }
+        };
+
+        /// <summary>
+        /// Slot 3: Better odds for rare+ cards.
+        /// </summary>
+        public static PackSlot RareSlot => new PackSlot
+        {
+            UseRarityWeights = true,
+            RarityWeights = new Dictionary<string, float>
+            {
+                { "Common", 30f },
+                { "Uncommon", 60f },
+                { "Rare", 60f },
+                { "Very Rare", 20f },
+                { "Ultra Rare", 5f },
+                { "Legendary", 5f }
+            }
+        };
+
+        /// <summary>
+        /// Gets the default slots for an auto-generated pack (3 slots).
+        /// </summary>
+        public static List<PackSlot> GetDefaultSlots()
+        {
+            return new List<PackSlot>
+            {
+                CommonSlot,
+                UncommonSlot,
+                RareSlot
+            };
+        }
+    }
+}

src/ModBehaviour.cs

@@ -17,6 +17,42 @@ namespace TradingCardMod
         private static ModBehaviour? _instance;
         public static ModBehaviour Instance => _instance!;
 
+        /// <summary>
+        /// Gets the list of registered card items (for loot injection).
+        /// </summary>
+        public List<Item> GetRegisteredItems() => _registeredItems;
+
+        /// <summary>
+        /// Gets cards for a specific set (used by PackUsageBehavior).
+        /// </summary>
+        public List<TradingCard> GetCardsBySet(string setName)
+        {
+            if (_cardsBySet.TryGetValue(setName, out var cards))
+            {
+                return cards;
+            }
+            return new List<TradingCard>();
+        }
+
+        /// <summary>
+        /// Gets the card name to TypeID mapping (used by PackUsageBehavior).
+        /// </summary>
+        public Dictionary<string, int> GetCardTypeIds() => _cardNameToTypeId;
+
+        /// <summary>
+        /// Gets slot configuration for a specific pack (used by PackUsageBehavior).
+        /// </summary>
+        public List<PackSlot> GetPackSlots(string setName, string packName)
+        {
+            string key = $"{setName}|{packName}";
+            if (_packDefinitions.TryGetValue(key, out var pack))
+            {
+                return pack.Slots;
+            }
+            Debug.LogWarning($"[TradingCardMod] Pack definition not found: {key}");
+            return new List<PackSlot>();
+        }
+
         // Base game item ID to clone (135 is commonly used for collectibles)
         private const int BASE_ITEM_ID = 135;
 
@@ -32,6 +68,14 @@ namespace TradingCardMod
         private Item? _binderItem;
         private Item? _cardBoxItem;
 
+        // Track cards and IDs per set for pack creation
+        private Dictionary<string, List<TradingCard>> _cardsBySet = new Dictionary<string, List<TradingCard>>();
+        private Dictionary<string, int> _cardNameToTypeId = new Dictionary<string, int>();
+        private List<Item> _registeredPacks = new List<Item>();
+
+        // Store pack definitions for runtime lookup (key = "SetName|PackName")
+        private Dictionary<string, CardPack> _packDefinitions = new Dictionary<string, CardPack>();
+
         // Debug: track spawn cycling
         private int _debugSpawnIndex = 0;
         private List<Item> _allSpawnableItems = new List<Item>();
@@ -54,6 +98,9 @@ namespace TradingCardMod
 
             try
             {
+                // Log all available tags for reference
+                TagHelper.LogAvailableTags();
+
                 // Create our custom tag first
                 _tradingCardTag = TagHelper.GetOrCreateTradingCardTag();
 
@@ -63,10 +110,14 @@ namespace TradingCardMod
                 // Create storage items
                 CreateStorageItems();
 
-                // Build spawnable items list (cards + storage)
+                // Create card packs
+                CreateCardPacks();
+
+                // Build spawnable items list (cards + storage + packs)
                 _allSpawnableItems.AddRange(_registeredItems);
                 if (_binderItem != null) _allSpawnableItems.Add(_binderItem);
                 if (_cardBoxItem != null) _allSpawnableItems.Add(_cardBoxItem);
+                _allSpawnableItems.AddRange(_registeredPacks);
 
                 Debug.Log("[TradingCardMod] Mod initialized successfully!");
             }
@@ -102,6 +153,34 @@ namespace TradingCardMod
             Debug.Log($"[TradingCardMod] Total cards loaded: {_loadedCards.Count}");
             Debug.Log($"[TradingCardMod] Total items registered: {_registeredItems.Count}");
             Debug.Log("[TradingCardMod] DEBUG: Press F9 to spawn items (cycles through cards, then binder, then box)");
+
+            // Clear the search cache so our items can be found
+            ClearSearchCache();
+        }
+
+        /// <summary>
+        /// Clears the ItemAssetsCollection search cache so dynamically registered items can be found.
+        /// </summary>
+        private void ClearSearchCache()
+        {
+            try
+            {
+                var cacheField = typeof(ItemAssetsCollection).GetField("cachedSearchResults",
+                    System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
+                if (cacheField != null)
+                {
+                    var cache = cacheField.GetValue(null) as System.Collections.IDictionary;
+                    if (cache != null)
+                    {
+                        cache.Clear();
+                        Debug.Log("[TradingCardMod] Cleared search cache for loot table integration");
+                    }
+                }
+            }
+            catch (Exception ex)
+            {
+                Debug.LogWarning($"[TradingCardMod] Could not clear search cache: {ex.Message}");
+            }
         }
 
         /// <summary>
@@ -138,6 +217,61 @@ namespace TradingCardMod
             );
         }
 
+        /// <summary>
+        /// Creates card packs for each loaded card set.
+        /// </summary>
+        private void CreateCardPacks()
+        {
+            foreach (var setEntry in _cardsBySet)
+            {
+                string setName = setEntry.Key;
+                var cards = setEntry.Value;
+
+                if (cards.Count == 0)
+                {
+                    Debug.LogWarning($"[TradingCardMod] No cards in set {setName}, skipping pack creation");
+                    continue;
+                }
+
+                // Create default pack for this set
+                string setDirectory = Path.Combine(_modPath, "CardSets", setName);
+                string imagesDirectory = Path.Combine(setDirectory, "images");
+
+                CardPack defaultPack = PackParser.CreateDefaultPack(setName, imagesDirectory);
+
+                // Check for user-defined packs
+                string packsFile = Path.Combine(setDirectory, "packs.txt");
+                var userPacks = PackParser.ParseFile(packsFile, setName, imagesDirectory);
+
+                // Create all packs
+                var allPacks = new List<CardPack> { defaultPack };
+                allPacks.AddRange(userPacks);
+
+                foreach (var pack in allPacks)
+                {
+                    // Store pack definition for runtime lookup
+                    string packKey = $"{pack.SetName}|{pack.PackName}";
+                    _packDefinitions[packKey] = pack;
+
+                    // Load pack icon
+                    Sprite? packIcon = null;
+                    if (File.Exists(pack.ImagePath))
+                    {
+                        packIcon = LoadSpriteFromFile(pack.ImagePath, pack.GenerateTypeID());
+                    }
+
+                    // Create pack item
+                    Item? packItem = PackHelper.CreatePackItem(pack, packIcon);
+                    if (packItem != null)
+                    {
+                        _registeredPacks.Add(packItem);
+                    }
+                }
+            }
+
+            Debug.Log($"[TradingCardMod] Created {_registeredPacks.Count} card packs");
+        }
+
         /// <summary>
         /// Update is called every frame. Used for debug input handling.
         /// </summary>
@@ -162,14 +296,23 @@ namespace TradingCardMod
             }
 
             // Cycle through all spawnable items
-            Item itemToSpawn = _allSpawnableItems[_debugSpawnIndex % _allSpawnableItems.Count];
+            Item prefab = _allSpawnableItems[_debugSpawnIndex % _allSpawnableItems.Count];
             _debugSpawnIndex++;
 
             try
             {
-                // Use game's utility to give item to player
-                ItemUtilities.SendToPlayer(itemToSpawn);
-                Debug.Log($"[TradingCardMod] Spawned: {itemToSpawn.DisplayName} (ID: {itemToSpawn.TypeID})");
+                // Instantiate a fresh copy of the item (don't send prefab directly)
+                Item instance = ItemAssetsCollection.InstantiateSync(prefab.TypeID);
+                if (instance != null)
+                {
+                    // Use game's utility to give item to player
+                    ItemUtilities.SendToPlayer(instance);
+                    Debug.Log($"[TradingCardMod] Spawned: {instance.DisplayName} (ID: {instance.TypeID})");
+                }
+                else
+                {
+                    Debug.LogError($"[TradingCardMod] Failed to instantiate {prefab.DisplayName} (ID: {prefab.TypeID})");
+                }
             }
             catch (Exception ex)
             {
@@ -200,6 +343,12 @@ namespace TradingCardMod
                 string imagesDirectory = Path.Combine(setDirectory, "images");
                 var cards = CardParser.ParseFile(cardsFile, imagesDirectory);
 
+                // Initialize set tracking
+                if (!_cardsBySet.ContainsKey(setName))
+                {
+                    _cardsBySet[setName] = new List<TradingCard>();
+                }
+
                 foreach (var card in cards)
                 {
                     // Validate card
@@ -214,6 +363,7 @@ namespace TradingCardMod
                     }
 
                     _loadedCards.Add(card);
+                    _cardsBySet[setName].Add(card);
 
                     // Register card as game item
                     RegisterCardWithGame(card);
@@ -261,12 +411,14 @@ namespace TradingCardMod
 
                 item.SetPrivateField("typeID", typeId);
                 item.SetPrivateField("weight", card.Weight);
-                item.SetPrivateField("value", card.Value);
                 item.SetPrivateField("displayName", locKey);
-                item.SetPrivateField("quality", card.GetQuality());
                 item.SetPrivateField("order", 0);
                 item.SetPrivateField("maxStackCount", 1);
 
+                // Use public setters for properties that have them
+                item.Value = card.Value;
+                item.Quality = card.GetQuality();
+
                 // Set display quality based on rarity
                 SetDisplayQuality(item, card.GetQuality());
 
@@ -280,6 +432,25 @@ namespace TradingCardMod
                     item.Tags.Add(luxuryTag);
                 }
 
+                // ============================================================
+                // TODO: REMOVE BEFORE RELEASE - TEST TAGS FOR LOOT SPAWNING
+                // These tags make cards appear frequently in loot for testing.
+                // Replace with appropriate tags (Collection, Misc, etc.) or
+                // implement proper loot table integration before shipping.
+                // ============================================================
+                Tag? medicTag = TagHelper.GetTargetTag("Medic");
+                if (medicTag != null)
+                {
+                    item.Tags.Add(medicTag);
+                }
+
+                Tag? toolTag = TagHelper.GetTargetTag("Tool");
+                if (toolTag != null)
+                {
+                    item.Tags.Add(toolTag);
+                }
+                // ============================================================
+
                 // Add our custom TradingCard tag
                 if (_tradingCardTag != null)
                 {
@@ -305,6 +476,7 @@ namespace TradingCardMod
                 if (ItemAssetsCollection.AddDynamicEntry(item))
                 {
                     _registeredItems.Add(item);
+                    _cardNameToTypeId[card.CardName] = typeId;
                     Debug.Log($"[TradingCardMod] Registered: {card.CardName} (ID: {typeId})");
                 }
                 else
@@ -440,10 +612,17 @@ namespace TradingCardMod
             // Clean up storage items
             StorageHelper.Cleanup();
 
+            // Clean up packs
+            PackHelper.Cleanup();
+
             // Clean up tags
             TagHelper.Cleanup();
 
             _loadedCards.Clear();
+            _cardsBySet.Clear();
+            _cardNameToTypeId.Clear();
+            _registeredPacks.Clear();
+            _packDefinitions.Clear();
             _allSpawnableItems.Clear();
 
             Debug.Log("[TradingCardMod] Cleanup complete.");

src/PackHelper.cs

@@ -0,0 +1,168 @@
+using System;
+using System.Collections.Generic;
+using UnityEngine;
+using ItemStatsSystem;
+using SodaCraft.Localizations;
+using Duckov.Utilities;
+
+namespace TradingCardMod
+{
+    /// <summary>
+    /// Helper class for creating card pack items.
+    /// </summary>
+    public static class PackHelper
+    {
+        // Base item to clone for packs (same as cards)
+        private const int BASE_ITEM_ID = 135;
+
+        // Track created packs for cleanup
+        private static readonly List<Item> _createdPacks = new List<Item>();
+        private static readonly List<GameObject> _createdGameObjects = new List<GameObject>();
+
+        /// <summary>
+        /// Creates a card pack item with gacha functionality.
+        /// </summary>
+        public static Item? CreatePackItem(
+            CardPack pack,
+            Sprite? icon = null)
+        {
+            try
+            {
+                // Get base item to clone
+                Item original = ItemAssetsCollection.GetPrefab(BASE_ITEM_ID);
+                if (original == null)
+                {
+                    Debug.LogError($"[TradingCardMod] Base item ID {BASE_ITEM_ID} not found for pack!");
+                    return null;
+                }
+
+                // Clone the item
+                GameObject clone = UnityEngine.Object.Instantiate(original.gameObject);
+                clone.name = $"CardPack_{pack.SetName}_{pack.PackName}";
+                UnityEngine.Object.DontDestroyOnLoad(clone);
+                _createdGameObjects.Add(clone);
+
+                Item item = clone.GetComponent<Item>();
+                if (item == null)
+                {
+                    Debug.LogError("[TradingCardMod] Cloned pack object has no Item component!");
+                    return null;
+                }
+
+                // Set item properties
+                int typeId = pack.GenerateTypeID();
+                string locKey = $"TC_Pack_{pack.SetName}_{pack.PackName}".Replace(" ", "_");
+
+                item.SetPrivateField("typeID", typeId);
+                item.SetPrivateField("weight", pack.Weight);
+                item.SetPrivateField("displayName", locKey);
+                item.SetPrivateField("order", 0);
+                item.SetPrivateField("maxStackCount", 10); // Packs can stack
+
+                // Use public setters
+                item.Value = pack.Value;
+                item.Quality = 3; // Uncommon quality for packs
+                item.DisplayQuality = (DisplayQuality)3;
+
+                // Set tags
+                item.Tags.Clear();
+
+                // Add Misc tag for loot spawning
+                Tag? miscTag = TagHelper.GetTargetTag("Misc");
+                if (miscTag != null)
+                {
+                    item.Tags.Add(miscTag);
+                }
+
+                // Set icon if provided
+                if (icon != null)
+                {
+                    item.SetPrivateField("icon", icon);
+                }
+
+                // Set up UsageUtilities for the "Use" context menu
+                // First, get or create UsageUtilities component
+                UsageUtilities usageUtils = clone.GetComponent<UsageUtilities>();
+                if (usageUtils == null)
+                {
+                    usageUtils = clone.AddComponent<UsageUtilities>();
+                }
+
+                // Clear any existing behaviors from the cloned base item
+                usageUtils.behaviors.Clear();
+
+                // Add our custom usage behavior for gacha
+                var usageBehavior = clone.AddComponent<PackUsageBehavior>();
+                usageBehavior.SetName = pack.SetName;
+                usageBehavior.PackName = pack.PackName;
+                // Note: Slots, AvailableCards, and CardTypeIds are looked up at runtime via ModBehaviour
+
+                // Register our behavior with UsageUtilities
+                usageUtils.behaviors.Add(usageBehavior);
+
+                // Set the Item's usageUtilities field to enable the Use option
+                item.SetPrivateField("usageUtilities", usageUtils);
+
+                // Set localization
+                LocalizationManager.SetOverrideText(locKey, pack.PackName);
+                string slotDesc = pack.Slots.Count == 1 ? "1 card" : $"{pack.Slots.Count} cards";
+                LocalizationManager.SetOverrideText($"{locKey}_Desc",
+                    $"Open to receive {slotDesc} from {pack.SetName}");
+
+                // Register with game
+                if (ItemAssetsCollection.AddDynamicEntry(item))
+                {
+                    _createdPacks.Add(item);
+                    Debug.Log($"[TradingCardMod] Registered pack: {pack.PackName} (ID: {typeId}, Slots: {pack.Slots.Count})");
+                    return item;
+                }
+                else
+                {
+                    Debug.LogError($"[TradingCardMod] Failed to register pack {pack.PackName}!");
+                    UnityEngine.Object.Destroy(clone);
+                    _createdGameObjects.Remove(clone);
+                    return null;
+                }
+            }
+            catch (Exception ex)
+            {
+                Debug.LogError($"[TradingCardMod] Error creating pack {pack.PackName}: {ex.Message}");
+                return null;
+            }
+        }
+
+        /// <summary>
+        /// Gets all pack items created by this helper.
+        /// </summary>
+        public static IReadOnlyList<Item> GetCreatedPacks()
+        {
+            return _createdPacks.AsReadOnly();
+        }
+
+        /// <summary>
+        /// Cleans up all packs created by this helper.
+        /// </summary>
+        public static void Cleanup()
+        {
+            foreach (var item in _createdPacks)
+            {
+                if (item != null)
+                {
+                    ItemAssetsCollection.RemoveDynamicEntry(item);
+                }
+            }
+            _createdPacks.Clear();
+
+            foreach (var go in _createdGameObjects)
+            {
+                if (go != null)
+                {
+                    UnityEngine.Object.Destroy(go);
+                }
+            }
+            _createdGameObjects.Clear();
+
+            Debug.Log("[TradingCardMod] PackHelper cleaned up.");
+        }
+    }
+}

src/PackParser.cs

@@ -0,0 +1,233 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace TradingCardMod
+{
+    /// <summary>
+    /// Parses pack definition files (packs.txt) into CardPack objects.
+    /// </summary>
+    public static class PackParser
+    {
+        /// <summary>
+        /// Parses a packs.txt file into a list of CardPack objects.
+        /// </summary>
+        /// <param name="filePath">Path to the packs.txt file.</param>
+        /// <param name="setName">The card set name these packs belong to.</param>
+        /// <param name="imagesDirectory">Directory containing pack images.</param>
+        /// <returns>List of parsed CardPack objects.</returns>
+        public static List<CardPack> ParseFile(string filePath, string setName, string imagesDirectory)
+        {
+            var packs = new List<CardPack>();
+
+            if (!File.Exists(filePath))
+            {
+                return packs;
+            }
+
+            string[] lines = File.ReadAllLines(filePath);
+            CardPack? currentPack = null;
+
+            for (int i = 0; i < lines.Length; i++)
+            {
+                string line = lines[i];
+                string trimmedLine = line.Trim();
+
+                // Skip empty lines and comments
+                if (string.IsNullOrWhiteSpace(trimmedLine) || trimmedLine.StartsWith("#"))
+                {
+                    continue;
+                }
+
+                // Check if this is a slot definition (indented line)
+                bool isIndented = line.StartsWith("  ") || line.StartsWith("\t");
+
+                if (isIndented && currentPack != null)
+                {
+                    // Parse slot definition
+                    PackSlot? slot = ParseSlotLine(trimmedLine);
+                    if (slot != null)
+                    {
+                        currentPack.Slots.Add(slot);
+                    }
+                }
+                else if (!isIndented)
+                {
+                    // Parse pack header line
+                    CardPack? pack = ParsePackHeader(trimmedLine, setName, imagesDirectory);
+                    if (pack != null)
+                    {
+                        if (currentPack != null)
+                        {
+                            packs.Add(currentPack);
+                        }
+                        currentPack = pack;
+                    }
+                }
+            }
+
+            // Don't forget the last pack
+            if (currentPack != null)
+            {
+                packs.Add(currentPack);
+            }
+
+            return packs;
+        }
+
+        /// <summary>
+        /// Parses a pack header line.
+        /// Format: PackName | Image | Value
+        /// </summary>
+        private static CardPack? ParsePackHeader(string line, string setName, string imagesDirectory)
+        {
+            string[] parts = line.Split('|');
+
+            if (parts.Length < 3)
+            {
+                return null;
+            }
+
+            string packName = parts[0].Trim();
+            string imageFile = parts[1].Trim();
+
+            if (!int.TryParse(parts[2].Trim(), out int value))
+            {
+                value = 100;
+            }
+
+            float weight = 0.1f;
+            if (parts.Length >= 4 && float.TryParse(parts[3].Trim(), out float parsedWeight))
+            {
+                weight = parsedWeight;
+            }
+
+            return new CardPack
+            {
+                PackName = packName,
+                SetName = setName,
+                ImageFile = imageFile,
+                ImagePath = Path.Combine(imagesDirectory, imageFile),
+                Value = value,
+                Weight = weight,
+                IsDefault = false
+            };
+        }
+
+        /// <summary>
+        /// Parses a slot definition line.
+        /// Format: RARITY: Common:100, Uncommon:50, Rare:10
+        ///     or: CARDS: CardName:100, CardName:50
+        /// </summary>
+        private static PackSlot? ParseSlotLine(string line)
+        {
+            var slot = new PackSlot();
+
+            if (line.StartsWith("RARITY:", StringComparison.OrdinalIgnoreCase))
+            {
+                slot.UseRarityWeights = true;
+                string weightsStr = line.Substring(7).Trim();
+                slot.RarityWeights = ParseWeights(weightsStr);
+            }
+            else if (line.StartsWith("CARDS:", StringComparison.OrdinalIgnoreCase))
+            {
+                slot.UseRarityWeights = false;
+                string weightsStr = line.Substring(6).Trim();
+                slot.CardWeights = ParseWeights(weightsStr);
+            }
+            else
+            {
+                // Default to rarity weights if no prefix
+                slot.UseRarityWeights = true;
+                slot.RarityWeights = ParseWeights(line);
+            }
+
+            return slot;
+        }
+
+        /// <summary>
+        /// Parses a comma-separated list of Name:Weight pairs.
+        /// </summary>
+        private static Dictionary<string, float> ParseWeights(string weightsStr)
+        {
+            var weights = new Dictionary<string, float>();
+
+            string[] pairs = weightsStr.Split(',');
+            foreach (string pair in pairs)
+            {
+                string[] keyValue = pair.Split(':');
+                if (keyValue.Length == 2)
+                {
+                    string key = keyValue[0].Trim();
+                    if (float.TryParse(keyValue[1].Trim(), out float weight))
+                    {
+                        weights[key] = weight;
+                    }
+                }
+            }
+
+            return weights;
+        }
+
+        /// <summary>
+        /// Creates a default pack for a card set.
+        /// </summary>
+        /// <param name="setName">The card set name.</param>
+        /// <param name="imagesDirectory">Directory for pack images.</param>
+        /// <returns>A default CardPack with standard slot weights.</returns>
+        public static CardPack CreateDefaultPack(string setName, string imagesDirectory)
+        {
+            string packName = $"{setName} Pack";
+            string imageFile = "pack.png";
+
+            return new CardPack
+            {
+                PackName = packName,
+                SetName = setName,
+                ImageFile = imageFile,
+                ImagePath = Path.Combine(imagesDirectory, imageFile),
+                Value = 100,
+                Weight = 0.1f,
+                IsDefault = true,
+                Slots = DefaultPackSlots.GetDefaultSlots()
+            };
+        }
+
+        /// <summary>
+        /// Validates a CardPack and returns any errors found.
+        /// </summary>
+        public static List<string> ValidatePack(CardPack pack)
+        {
+            var errors = new List<string>();
+
+            if (string.IsNullOrWhiteSpace(pack.PackName))
+            {
+                errors.Add("Pack name is required");
+            }
+
+            if (pack.Slots.Count == 0)
+            {
+                errors.Add("Pack must have at least one slot");
+            }
+
+            foreach (var slot in pack.Slots)
+            {
+                if (slot.UseRarityWeights && slot.RarityWeights.Count == 0)
+                {
+                    errors.Add("Rarity slot must have at least one weight defined");
+                }
+                else if (!slot.UseRarityWeights && slot.CardWeights.Count == 0)
+                {
+                    errors.Add("Card slot must have at least one card defined");
+                }
+            }
+
+            if (pack.Value < 0)
+            {
+                errors.Add("Pack value must be non-negative");
+            }
+
+            return errors;
+        }
+    }
+}

src/PackUsageBehavior.cs

@@ -0,0 +1,252 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Cysharp.Threading.Tasks;
+using ItemStatsSystem;
+using UnityEngine;
+
+namespace TradingCardMod
+{
+    /// <summary>
+    /// Custom usage behavior for card packs that generates multiple cards based on slot weights.
+    /// </summary>
+    public class PackUsageBehavior : UsageBehavior
+    {
+        /// <summary>
+        /// The card set this pack draws from.
+        /// </summary>
+        public string SetName = string.Empty;
+
+        /// <summary>
+        /// The pack name within the set (for looking up slot config).
+        /// </summary>
+        public string PackName = string.Empty;
+
+        private bool _running;
+
+        /// <summary>
+        /// Gets available cards for this set from ModBehaviour.
+        /// </summary>
+        private List<TradingCard> GetAvailableCards()
+        {
+            if (ModBehaviour.Instance == null) return new List<TradingCard>();
+            return ModBehaviour.Instance.GetCardsBySet(SetName);
+        }
+
+        /// <summary>
+        /// Gets card type IDs from ModBehaviour.
+        /// </summary>
+        private Dictionary<string, int> GetCardTypeIds()
+        {
+            if (ModBehaviour.Instance == null) return new Dictionary<string, int>();
+            return ModBehaviour.Instance.GetCardTypeIds();
+        }
+
+        /// <summary>
+        /// Gets slot configuration from ModBehaviour.
+        /// </summary>
+        private List<PackSlot> GetSlots()
+        {
+            if (ModBehaviour.Instance == null) return new List<PackSlot>();
+            return ModBehaviour.Instance.GetPackSlots(SetName, PackName);
+        }
+
+        public override DisplaySettingsData DisplaySettings => new DisplaySettingsData
+        {
+            display = true,
+            description = $"Open to receive {GetSlots().Count} trading cards"
+        };
+
+        public override bool CanBeUsed(Item item, object user)
+        {
+            if (!(user is CharacterMainControl))
+            {
+                return false;
+            }
+            return true;
+        }
+
+        protected override void OnUse(Item item, object user)
+        {
+            CharacterMainControl character = user as CharacterMainControl;
+            var slots = GetSlots();
+            if (character != null && slots.Count > 0)
+            {
+                GenerateCards(item, character, slots).Forget();
+            }
+            else
+            {
+                Debug.LogWarning($"[TradingCardMod] Cannot open pack: character={character != null}, slots={slots.Count}");
+            }
+        }
+
+        private async UniTask GenerateCards(Item packItem, CharacterMainControl character, List<PackSlot> slots)
+        {
+            if (_running)
+            {
+                return;
+            }
+            _running = true;
+
+            var generatedCards = new List<string>();
+
+            try
+            {
+                foreach (var slot in slots)
+                {
+                    int? cardTypeId = RollSlot(slot);
+                    if (cardTypeId.HasValue)
+                    {
+                        Item card = await ItemAssetsCollection.InstantiateAsync(cardTypeId.Value);
+                        if (card != null)
+                        {
+                            string cardName = card.DisplayName;
+                            generatedCards.Add(cardName);
+
+                            bool pickedUp = character.PickupItem(card);
+                            if (!pickedUp && card != null)
+                            {
+                                if (card.ActiveAgent != null)
+                                {
+                                    card.AgentUtilities.ReleaseActiveAgent();
+                                }
+                                PlayerStorage.Push(card);
+                            }
+                        }
+                    }
+                }
+
+                // Show notification
+                if (generatedCards.Count > 0)
+                {
+                    string message = $"Received: {string.Join(", ", generatedCards)}";
+                    Debug.Log($"[TradingCardMod] Pack opened: {message}");
+                    // NotificationText.Push(message); // Uncomment if NotificationText is accessible
+                }
+
+                // Consume the pack after successfully generating cards
+                ConsumeItem(packItem);
+            }
+            catch (Exception ex)
+            {
+                Debug.LogError($"[TradingCardMod] Error generating cards from pack: {ex.Message}");
+            }
+
+            _running = false;
+        }
+
+        /// <summary>
+        /// Consumes one pack from the stack or detaches if only one left.
+        /// </summary>
+        private void ConsumeItem(Item item)
+        {
+            if (item == null) return;
+
+            if (item.StackCount > 1)
+            {
+                item.StackCount -= 1;
+            }
+            else
+            {
+                item.Detach();
+            }
+        }
+
+        /// <summary>
+        /// Rolls a single slot to determine which card to give.
+        /// </summary>
+        private int? RollSlot(PackSlot slot)
+        {
+            if (slot.UseRarityWeights)
+            {
+                return RollByRarity(slot.RarityWeights);
+            }
+            else
+            {
+                return RollByCardName(slot.CardWeights);
+            }
+        }
+
+        /// <summary>
+        /// Selects a card based on rarity weights.
+        /// </summary>
+        private int? RollByRarity(Dictionary<string, float> rarityWeights)
+        {
+            // Build weighted list of cards based on rarity
+            var weightedCards = new List<(int typeId, float weight)>();
+            var availableCards = GetAvailableCards();
+            var cardTypeIds = GetCardTypeIds();
+
+            foreach (var card in availableCards)
+            {
+                if (cardTypeIds.TryGetValue(card.CardName, out int typeId))
+                {
+                    // Get the weight for this card's rarity
+                    if (rarityWeights.TryGetValue(card.Rarity, out float weight) && weight > 0)
+                    {
+                        weightedCards.Add((typeId, weight));
+                    }
+                }
+            }
+
+            if (weightedCards.Count == 0)
+            {
+                Debug.LogWarning($"[TradingCardMod] No cards available for rarity roll (set: {SetName}, cards: {availableCards.Count})");
+                return null;
+            }
+
+            return WeightedRandom(weightedCards);
+        }
+
+        /// <summary>
+        /// Selects a card based on specific card name weights.
+        /// </summary>
+        private int? RollByCardName(Dictionary<string, float> cardWeights)
+        {
+            var weightedCards = new List<(int typeId, float weight)>();
+            var cardTypeIds = GetCardTypeIds();
+
+            foreach (var kvp in cardWeights)
+            {
+                if (cardTypeIds.TryGetValue(kvp.Key, out int typeId))
+                {
+                    weightedCards.Add((typeId, kvp.Value));
+                }
+                else
+                {
+                    Debug.LogWarning($"[TradingCardMod] Card '{kvp.Key}' not found for pack slot");
+                }
+            }
+
+            if (weightedCards.Count == 0)
+            {
+                Debug.LogWarning("[TradingCardMod] No cards available for card name roll");
+                return null;
+            }
+
+            return WeightedRandom(weightedCards);
+        }
+
+        /// <summary>
+        /// Performs weighted random selection.
+        /// </summary>
+        private int WeightedRandom(List<(int typeId, float weight)> items)
+        {
+            float totalWeight = items.Sum(x => x.weight);
+            float roll = UnityEngine.Random.Range(0f, totalWeight);
+
+            float cumulative = 0f;
+            foreach (var item in items)
+            {
+                cumulative += item.weight;
+                if (roll <= cumulative)
+                {
+                    return item.typeId;
+                }
+            }
+
+            // Fallback to last item
+            return items[items.Count - 1].typeId;
+        }
+    }
+}

src/Patches.cs

@@ -74,4 +74,7 @@ namespace TradingCardMod
             }
         }
     }
+
+    // Search injection patch disabled - causing index errors
+    // TODO: Find better approach for loot table integration
 }