feat: Enemies drop loot on death

src/engine/systems/LootSystem.ts

@@ -0,0 +1,166 @@
+import { type Item, type ActorType } from "../../core/types";
+import { 
+  createMeleeWeapon, 
+  createArmour, 
+  createConsumable,
+  createAmmo,
+  MELEE_WEAPONS,
+  ARMOUR
+} from "../../core/config/Items";
+import { 
+  WEAPON_VARIANTS, 
+  ARMOUR_VARIANTS,
+  type WeaponVariantId,
+  type ArmourVariantId
+} from "../../core/config/ItemVariants";
+import { UpgradeManager } from "../systems/UpgradeManager";
+
+/**
+ * Loot drop configuration.
+ * Chances are cumulative (checked in order).
+ */
+export const LOOT_CONFIG = {
+  // Base chance any item drops at all (per enemy)
+  baseDropChance: 0.25,
+
+  // Type weights (what kind of item drops)
+  typeWeights: {
+    weapon: 30,
+    armour: 25,
+    consumable: 35,
+    ammo: 10,
+  },
+
+  // Rarity chances (applied after type is chosen)
+  rarityChances: {
+    base: 0.60,        // 60% just base item
+    variant: 0.30,     // 30% has a variant
+    upgraded: 0.10,    // 10% has upgrade applied
+  },
+
+  // Per-enemy type drop chance modifiers
+  enemyDropModifiers: {
+    rat: 0.8,
+    bat: 0.9,
+    // Add more enemy types as needed
+  } as Record<ActorType, number>,
+};
+
+/**
+ * Generate a random loot item based on the loot configuration.
+ * Returns null if no item drops.
+ */
+export function generateLoot(
+  random: () => number, 
+  enemyType?: ActorType,
+  floorLevel: number = 1
+): Item | null {
+  // Check base drop chance (modified by enemy type)
+  let dropChance: number = LOOT_CONFIG.baseDropChance;
+  if (enemyType && LOOT_CONFIG.enemyDropModifiers[enemyType]) {
+    dropChance *= LOOT_CONFIG.enemyDropModifiers[enemyType];
+  }
+  
+  // Higher floor = slightly more drops
+  dropChance += floorLevel * 0.02;
+  dropChance = Math.min(dropChance, 0.6); // Cap at 60%
+
+  if (random() > dropChance) {
+    return null;
+  }
+
+  // Determine item type
+  const itemType = pickWeightedRandom(LOOT_CONFIG.typeWeights, random);
+
+  // Determine rarity tier
+  const rarityRoll = random();
+  let hasVariant = false;
+  let hasUpgrade = false;
+
+  if (rarityRoll >= (1 - LOOT_CONFIG.rarityChances.upgraded)) {
+    // Top 10%: upgraded (implies has variant too)
+    hasVariant = true;
+    hasUpgrade = true;
+  } else if (rarityRoll >= (1 - LOOT_CONFIG.rarityChances.upgraded - LOOT_CONFIG.rarityChances.variant)) {
+    // Next 30%: variant only
+    hasVariant = true;
+  }
+  // Otherwise: base item (60%)
+
+  // Generate the item
+  let item: Item | null = null;
+
+  switch (itemType) {
+    case "weapon": {
+      const weaponIds = Object.keys(MELEE_WEAPONS) as (keyof typeof MELEE_WEAPONS)[];
+      const weaponId = weaponIds[Math.floor(random() * weaponIds.length)];
+      
+      let variant: WeaponVariantId | undefined;
+      if (hasVariant) {
+        const variantIds = Object.keys(WEAPON_VARIANTS) as WeaponVariantId[];
+        variant = variantIds[Math.floor(random() * variantIds.length)];
+      }
+      
+      item = createMeleeWeapon(weaponId, variant);
+      break;
+    }
+    
+    case "armour": {
+      const armourIds = Object.keys(ARMOUR) as (keyof typeof ARMOUR)[];
+      const armourId = armourIds[Math.floor(random() * armourIds.length)];
+      
+      let variant: ArmourVariantId | undefined;
+      if (hasVariant) {
+        const variantIds = Object.keys(ARMOUR_VARIANTS) as ArmourVariantId[];
+        variant = variantIds[Math.floor(random() * variantIds.length)];
+      }
+      
+      item = createArmour(armourId, variant);
+      break;
+    }
+    
+    case "consumable": {
+      // Only drop health potions and throwing daggers, not upgrade scrolls
+      const droppableConsumables = ["health_potion", "throwing_dagger"] as const;
+      const consumableId = droppableConsumables[Math.floor(random() * droppableConsumables.length)];
+      const quantity = 1 + Math.floor(random() * 2); // 1-2
+      
+      item = createConsumable(consumableId, quantity);
+      break;
+    }
+    
+    case "ammo": {
+      const quantity = 5 + Math.floor(random() * 10); // 5-14
+      item = createAmmo("ammo_9mm", quantity);
+      break;
+    }
+  }
+
+  // Apply upgrade if rolled
+  if (item && hasUpgrade) {
+    UpgradeManager.applyUpgrade(item);
+  }
+
+  return item;
+}
+
+/**
+ * Pick from weighted options.
+ */
+function pickWeightedRandom(
+  weights: Record<string, number>, 
+  random: () => number
+): string {
+  const entries = Object.entries(weights);
+  const total = entries.reduce((sum, [, w]) => sum + w, 0);
+  let roll = random() * total;
+  
+  for (const [key, weight] of entries) {
+    roll -= weight;
+    if (roll <= 0) {
+      return key;
+    }
+  }
+  
+  return entries[entries.length - 1][0];
+}

src/scenes/GameScene.ts

@@ -29,6 +29,7 @@ import { SystemRegistry } from "../engine/ecs/System";
 import { TriggerSystem } from "../engine/ecs/systems/TriggerSystem";
 import { StatusEffectSystem } from "../engine/ecs/systems/StatusEffectSystem";
 import { EventBus } from "../engine/ecs/EventBus";
+import { generateLoot } from "../engine/systems/LootSystem";
 
 export class GameScene extends Phaser.Scene {
   private world!: World;
@@ -690,6 +691,15 @@ export class GameScene extends Phaser.Scene {
          this.dungeonRenderer.showHeal(ev.x, ev.y, ev.amount);
       } else if (ev.type === "killed") {
          this.dungeonRenderer.spawnCorpse(ev.x, ev.y, ev.victimType || "rat");
+         
+         // Try to drop loot from killed enemy
+         if (ev.victimType && ev.victimType !== "player") {
+           const loot = generateLoot(Math.random, ev.victimType, this.floorIndex);
+           if (loot) {
+             this.itemManager.spawnItem(loot, { x: ev.x, y: ev.y });
+             this.dungeonRenderer.showFloatingText(ev.x, ev.y, `${loot.name}!`, "#ffd700");
+           }
+         }
       } else if (ev.type === "waited" && ev.actorId === this.playerId) {
          const player = this.world.actors.get(this.playerId) as CombatantActor;
          if (player) {