feat: add milestone prestige bonuses every 5th prestige

Every 5th prestige awards a scaling runestone windfall:
milestone_number * 25 stones (prestige 5 = 25, 10 = 50, 50 = 250, etc).
Shown in the ascension success message when non-zero.

IDEAS.md

@@ -12,7 +12,7 @@ A running list of planned features and content additions. Strike through items a
 
 - [x] **Daily challenges** — Three rotating objectives each day (e.g. kill X boss, earn X gold this run, complete X quests). Reward bonus crystals. Encourages daily logins even when idling comfortably.
 
-- [ ] **Boss first-kill bounties** — Defeating a boss for the very first time grants a one-time runestone bonus. Rewards exploration and makes conquering a new zone feel extra satisfying.
+- [x] **Boss first-kill bounties** — Defeating a boss for the very first time grants a one-time runestone bonus. Rewards exploration and makes conquering a new zone feel extra satisfying.
 
 - [ ] **Auto-prestige toggle** — Unlockable via the prestige shop. Automatically prestiges the moment the threshold is reached. Late-game convenience that dedicated players will love.
 
@@ -24,7 +24,7 @@ A running list of planned features and content additions. Strike through items a
 
 - [ ] **The Codex / Lore Book** — Defeating bosses and completing quests unlocks lore entries about the world. Pure flavour, but gives the world depth and a collection mechanic. Show a ✨ notification when new lore unlocks.
 
-- [ ] **Milestone prestige bonuses** — Every 5th prestige, earn a free prestige upgrade or a large runestone windfall. Gives players mini-goals within the prestige loop.
+- [x] **Milestone prestige bonuses** — Every 5th prestige, earn a free prestige upgrade or a large runestone windfall. Gives players mini-goals within the prestige loop.
 
 ---
 
@@ -41,8 +41,8 @@ A running list of planned features and content additions. Strike through items a
 1. ~~Offline earnings~~ ✅
 2. ~~Statistics panel~~ ✅
 3. ~~Daily challenges~~ ✅
-4. Boss first-kill bounties (easy content win)
+4. ~~Boss first-kill bounties~~ ✅
-5. Milestone prestige bonuses (easy content win)
+5. ~~Milestone prestige bonuses~~ ✅
 6. Equipment set bonuses (medium effort)
 7. Auto-prestige toggle (prestige shop upgrade)
 8. The Codex / Lore Book (flavour, lower priority)

apps/api/src/routes/prestige.ts

@@ -47,7 +47,7 @@ prestigeRouter.post("/", async (context) => {
     challengeCrystals = result.crystalsAwarded;
   }
 
-  const { newState, newPrestigeData, runestonesEarned } = buildPostPrestigeState(
+  const { newState, newPrestigeData, runestonesEarned, milestoneRunestones } = buildPostPrestigeState(
     state,
     characterName,
   );
@@ -81,6 +81,7 @@ prestigeRouter.post("/", async (context) => {
   return context.json({
     runestones: runestonesEarned,
     newPrestigeCount: newPrestigeData.count,
+    milestoneRunestones,
   });
 });
 

apps/api/src/services/prestige.ts

@@ -9,6 +9,8 @@ import { DEFAULT_PRESTIGE_UPGRADES } from "../data/prestigeUpgrades.js";
 const BASE_PRESTIGE_GOLD_THRESHOLD = 1_000_000;
 const THRESHOLD_SCALE_FACTOR = 5;
 const RUNESTONES_PER_PRESTIGE_LEVEL = 10;
+const MILESTONE_INTERVAL = 5;
+const MILESTONE_RUNESTONES_PER_INTERVAL = 25;
 
 /**
  * Calculates the gold threshold required for the next prestige.
@@ -65,6 +67,16 @@ export const calculateRunestones = (
 export const calculateProductionMultiplier = (prestigeCount: number): number =>
   Math.pow(1.15, prestigeCount);
 
+/**
+ * Returns the milestone runestone bonus for the given prestige count.
+ * Every MILESTONE_INTERVAL prestiges awards milestone_number * MILESTONE_RUNESTONES_PER_INTERVAL stones.
+ */
+export const calculateMilestoneBonus = (newPrestigeCount: number): number => {
+  if (newPrestigeCount % MILESTONE_INTERVAL !== 0) return 0;
+  const milestoneNumber = newPrestigeCount / MILESTONE_INTERVAL;
+  return milestoneNumber * MILESTONE_RUNESTONES_PER_INTERVAL;
+};
+
 /**
  * Generates the reset game state after a prestige.
  * Carries over prestige data and runestones; resets everything else.
@@ -72,7 +84,7 @@ export const calculateProductionMultiplier = (prestigeCount: number): number =>
 export const buildPostPrestigeState = (
   currentState: GameState,
   characterName: string,
-): { newState: GameState; newPrestigeData: PrestigeData; runestonesEarned: number } => {
+): { newState: GameState; newPrestigeData: PrestigeData; runestonesEarned: number; milestoneRunestones: number } => {
   const runestonesEarned = calculateRunestones(
     currentState.player.totalGoldEarned,
     currentState.prestige.count,
@@ -80,10 +92,11 @@ export const buildPostPrestigeState = (
   );
   const newPrestigeCount = currentState.prestige.count + 1;
   const { purchasedUpgradeIds } = currentState.prestige;
+  const milestoneRunestones = calculateMilestoneBonus(newPrestigeCount);
 
   const newPrestigeData: PrestigeData = {
     count: newPrestigeCount,
-    runestones: currentState.prestige.runestones + runestonesEarned,
+    runestones: currentState.prestige.runestones + runestonesEarned + milestoneRunestones,
     productionMultiplier: calculateProductionMultiplier(newPrestigeCount),
     purchasedUpgradeIds,
     lastPrestigedAt: Date.now(),
@@ -97,5 +110,5 @@ export const buildPostPrestigeState = (
     lastTickAt: Date.now(),
   };
 
-  return { newState, newPrestigeData, runestonesEarned };
+  return { newState, newPrestigeData, runestonesEarned, milestoneRunestones };
 };

apps/web/src/components/game/PrestigePanel.tsx

@@ -42,7 +42,7 @@ export const PrestigePanel = (): React.JSX.Element => {
   const { state, reload, formatNumber, buyPrestigeUpgrade } = useGame();
   const [characterName, setCharacterName] = useState("");
   const [isPending, setIsPending] = useState(false);
-  const [result, setResult] = useState<{ runestones: number; count: number } | null>(null);
+  const [result, setResult] = useState<{ runestones: number; count: number; milestoneRunestones: number } | null>(null);
   const [prestigeError, setPrestigeError] = useState<string | null>(null);
   const [buyingId, setBuyingId] = useState<string | null>(null);
   const [activeTab, setActiveTab] = useState<"prestige" | "shop">("prestige");
@@ -65,7 +65,7 @@ export const PrestigePanel = (): React.JSX.Element => {
     setPrestigeError(null);
     try {
       const data = await prestige({ characterName: characterName.trim() });
-      setResult({ runestones: data.runestones, count: data.newPrestigeCount });
+      setResult({ runestones: data.runestones, count: data.newPrestigeCount, milestoneRunestones: data.milestoneRunestones });
       await reload();
     } catch (err) {
       setPrestigeError(err instanceof Error ? err.message : "Prestige failed");
@@ -176,6 +176,9 @@ export const PrestigePanel = (): React.JSX.Element => {
               {result && (
                 <p className="success">
                   Ascended to Prestige {result.count}! Earned {formatNumber(result.runestones)} Runestones.
+                  {result.milestoneRunestones > 0 && (
+                    <> 🎉 Milestone bonus: +{formatNumber(result.milestoneRunestones)} Runestones!</>
+                  )}
                 </p>
               )}
             </div>

packages/types/src/interfaces/Api.ts

@@ -58,6 +58,8 @@ export interface BossChallengeResponse {
     crystals: number;
     upgradeIds: string[];
     equipmentIds: string[];
+    /** Runestone bounty awarded for defeating this boss for the very first time */
+    bountyRunestones: number;
   };
   casualties?: Array<{
     adventurerId: string;
@@ -72,6 +74,8 @@ export interface PrestigeRequest {
 export interface PrestigeResponse {
   runestones: number;
   newPrestigeCount: number;
+  /** Bonus runestones awarded for reaching a milestone prestige (every 5th), 0 if not a milestone */
+  milestoneRunestones: number;
 }
 
 export interface BuyPrestigeUpgradeRequest {