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I addressed these challenges through careful architecture and implementation:

• Server-Authoritative Architecture: The server maintains the single source of truth for game state. All player actions are sent to the server, validated, processed, and then broadcast to all clients. This prevents cheating and ensures consistency. The Game class encapsulates all game logic, with specialized handlers for dice, turns, state, players, AI, and lifecycle management.
• Modular Game Mode System: Implemented a base GameMode class with three concrete implementations (TraditionalGameMode, ModernGameMode, LimitedSupplyGameMode). Limited Supply mode uses a decorator pattern to wrap base modes, allowing combinations like Modern + Limited Supply. Each mode handles its own initialization, turn/round events, and game-specific logic.
• AI Persona System: Created multiple AI personas (Conservative Charles, Aggressive Alex, Balanced Bella, Dividend Diana, Speculative Sam) with distinct strategies. Each persona uses a strategy function that analyzes game state and makes decisions based on their personality. The GameAIHandler manages AI turn processing and integrates seamlessly with the game loop.
• Debounced Game State Persistence: Implemented automatic game state saving with 2-second debouncing to avoid excessive database writes. Games are serialized to JSONB and stored in PostgreSQL, allowing full game recovery after server restarts. The GameManager handles persistence and game lifecycle management.
• Multi-Player ELO Rating System: Implemented an ELO system that adjusts for game size using a logarithmic factor (fN = log2(N) / 3). The system handles edge cases like ties, AI players (excluded from ELO), and 2-player games. All rating updates use database transactions to ensure atomicity.
• Comprehensive Security Layers: Implemented JWT authentication with token expiration, rate limiting (200 req/15min API, 5 req/15min auth, 60 events/min Socket.IO), password security (bcrypt hashing, complexity requirements, history tracking to prevent reuse), input validation with express-validator, file upload security (magic byte checking, MIME type validation, size limits), and admin middleware for role-based access control.
• Socket.IO with Rooms & Reconnection: Used Socket.IO for WebSocket connections, which handles reconnection automatically and provides rooms for game sessions. Each game session is a Socket.IO room, making it easy to broadcast to all players in a game. The system handles player disconnections gracefully and restores state on reconnection.
• Efficient Achievement Calculation: The achievement system uses JSONB fields in PostgreSQL to store complex statistics efficiently. Achievements are calculated on-demand with caching of stat values to avoid repeated computation. The system tracks dozens of metrics including per-stock statistics, dice roll distributions, and game outcomes.

// Save game state to database (debounced)
async saveGameState(game, immediate = false) {
  // Skip saving completed games
  if (game.status === 'complete') {
    return;
  }

  // Debounce saves to avoid excessive database writes
  if (!immediate) {
    const existingTimer = this.saveDebounceTimers.get(game.id);
    if (existingTimer) {
      clearTimeout(existingTimer);
    }

    const timer = setTimeout(async () => {
      await this._saveGameState(game);
      this.saveDebounceTimers.delete(game.id);
    }, 2000); // Save 2 seconds after last change

    this.saveDebounceTimers.set(game.id, timer);
    return;
  }

  // Immediate save
  await this._saveGameState(game);
}