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.

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 };
 };