Initial scaffold: AI Tycoon monorepo with core game loop

Turborepo monorepo with three packages:
- packages/shared: TypeScript types for all 14 game systems + balance constants + formatting utils
- packages/game-engine: Pure TS simulation engine with tick processor, economy, infrastructure, compute, research, market, and reputation systems
- apps/web: React + Vite + Tailwind + Zustand frontend with sidebar dashboard layout, new game screen, dashboard with charts, infrastructure management, and model training pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/game-engine/src/engine.ts

@@ -0,0 +1,82 @@
+import type { GameState } from '@ai-tycoon/shared';
+import { processTick } from './tick';
+
+export interface GameEngineCallbacks {
+  getState: () => GameState;
+  setState: (partial: Partial<GameState>) => void;
+  onTick?: (tickCount: number) => void;
+  onEraChange?: (era: GameState['meta']['currentEra']) => void;
+}
+
+export class GameEngine {
+  private callbacks: GameEngineCallbacks;
+  private lastFrameTime = 0;
+  private accumulator = 0;
+  private animFrameId: number | null = null;
+  private tickIntervalMs = 1000;
+
+  constructor(callbacks: GameEngineCallbacks) {
+    this.callbacks = callbacks;
+  }
+
+  start(): void {
+    if (this.animFrameId !== null) return;
+    this.lastFrameTime = performance.now();
+    this.accumulator = 0;
+    this.loop(this.lastFrameTime);
+  }
+
+  stop(): void {
+    if (this.animFrameId !== null) {
+      cancelAnimationFrame(this.animFrameId);
+      this.animFrameId = null;
+    }
+  }
+
+  setSpeed(speed: number): void {
+    this.tickIntervalMs = 1000 / speed;
+  }
+
+  processOfflineTicks(missedTicks: number): { revenue: number; expenses: number; ticksProcessed: number } {
+    let totalRevenue = 0;
+    let totalExpenses = 0;
+
+    for (let i = 0; i < missedTicks; i++) {
+      const state = this.callbacks.getState();
+      const result = processTick(state);
+      this.callbacks.setState(result);
+      totalRevenue += result.economy?.revenuePerTick ?? 0;
+      totalExpenses += result.economy?.expensesPerTick ?? 0;
+    }
+
+    return { revenue: totalRevenue, expenses: totalExpenses, ticksProcessed: missedTicks };
+  }
+
+  private loop = (now: number): void => {
+    const delta = now - this.lastFrameTime;
+    this.lastFrameTime = now;
+
+    const state = this.callbacks.getState();
+    if (!state.meta.isPaused) {
+      this.accumulator += delta;
+
+      let ticksThisFrame = 0;
+      const maxTicksPerFrame = 10;
+
+      while (this.accumulator >= this.tickIntervalMs && ticksThisFrame < maxTicksPerFrame) {
+        const currentState = this.callbacks.getState();
+        const result = processTick(currentState);
+        this.callbacks.setState(result);
+        this.accumulator -= this.tickIntervalMs;
+        ticksThisFrame++;
+        this.callbacks.onTick?.(currentState.meta.tickCount + 1);
+      }
+
+      if (this.accumulator > this.tickIntervalMs * maxTicksPerFrame) {
+        this.accumulator = 0;
+      }
+    }
+
+    this.animFrameId = requestAnimationFrame(this.loop);
+  };
+}