GameEngine.cpp:
//-----------------------------------------------------------------
// Game Engine Object
// C++ Source - GameEngine.cpp
//-----------------------------------------------------------------

//-----------------------------------------------------------------
// Include Files
//-----------------------------------------------------------------
#include "GameEngine.h"

//-----------------------------------------------------------------
// Static Variable Initialization
//-----------------------------------------------------------------
GameEngine *GameEngine::m_pGameEngine = NULL;

//-----------------------------------------------------------------
// Windows Functions
//-----------------------------------------------------------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
  PSTR szCmdLine, int iCmdShow)
{
  MSG         msg;
  static int  iTickTrigger = 0;
  int         iTickCount;

  if (GameInitialize(hInstance))
  {
    // Initialize the game engine
    if (!GameEngine::GetEngine()->Initialize(iCmdShow))
      return FALSE;

    // Enter the main message loop
    while (TRUE)
    {
      if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
      {
        // Process the message
        if (msg.message == WM_QUIT)
          break;
        TranslateMessage(&msg);
        DispatchMessage(&msg);
      }
      else
      {
        // Make sure the game engine isn't sleeping
        if (!GameEngine::GetEngine()->GetSleep())
        {
          // Check the tick count to see if a game cycle has elapsed
          iTickCount = GetTickCount();
          if (iTickCount > iTickTrigger)
          {
            iTickTrigger = iTickCount +
              GameEngine::GetEngine()->GetFrameDelay();
            GameCycle();
          }
        }
      }
    }
    return (int)msg.wParam;
  }

  // End the game
  GameEnd();

  return TRUE;
}

LRESULT CALLBACK WndProc(HWND hWindow, UINT msg, WPARAM wParam, LPARAM lParam)
{
  // Route all Windows messages to the game engine
  return GameEngine::GetEngine()->HandleEvent(hWindow, msg, wParam, lParam);
}

//-----------------------------------------------------------------
// GameEngine Constructor(s)/Destructor
//-----------------------------------------------------------------
GameEngine::GameEngine(HINSTANCE hInstance, LPTSTR szWindowClass,
  LPTSTR szTitle, WORD wIcon, WORD wSmallIcon, int iWidth, int iHeight)
{
  // Set the member variables for the game engine
  m_pGameEngine = this;
  m_hInstance = hInstance;
  m_hWindow = NULL;
  if (lstrlen(szWindowClass) > 0)
    lstrcpy(m_szWindowClass, szWindowClass);
  if (lstrlen(szTitle) > 0)
    lstrcpy(m_szTitle, szTitle);
  m_wIcon = wIcon;
  m_wSmallIcon = wSmallIcon;
  m_iWidth = iWidth;
  m_iHeight = iHeight;
  m_iFrameDelay = 50;   // 20 FPS default
  m_bSleep = TRUE;
}

GameEngine::~GameEngine()
{
}

//-----------------------------------------------------------------
// Game Engine General Methods
//-----------------------------------------------------------------
BOOL GameEngine::Initialize(int iCmdShow)
{
  WNDCLASSEX    wndclass;

  // Create the window class for the main window
  wndclass.cbSize         = sizeof(wndclass);
  wndclass.style          = CS_HREDRAW | CS_VREDRAW;
  wndclass.lpfnWndProc    = WndProc;
  wndclass.cbClsExtra     = 0;
  wndclass.cbWndExtra     = 0;
  wndclass.hInstance      = m_hInstance;
  wndclass.hIcon          = LoadIcon(m_hInstance,
    MAKEINTRESOURCE(GetIcon()));
  wndclass.hIconSm        = LoadIcon(m_hInstance,
    MAKEINTRESOURCE(GetSmallIcon()));
  wndclass.hCursor        = LoadCursor(NULL, IDC_ARROW);
  wndclass.hbrBackground  = (HBRUSH)(COLOR_WINDOW + 1);
  wndclass.lpszMenuName   = NULL;
  wndclass.lpszClassName  = m_szWindowClass;

  // Register the window class
  if (!RegisterClassEx(&wndclass))
    return FALSE;

  // Calculate the window size and position based upon the game size
  int iWindowWidth = m_iWidth + GetSystemMetrics(SM_CXFIXEDFRAME) * 2,
      iWindowHeight = m_iHeight + GetSystemMetrics(SM_CYFIXEDFRAME) * 2       + GetSystemMetrics(SM_CYCAPTION);
  if (wndclass.lpszMenuName != NULL)
    iWindowHeight += GetSystemMetrics(SM_CYMENU);
  int iXWindowPos = (GetSystemMetrics(SM_CXSCREEN) - iWindowWidth) / 2,
      iYWindowPos = (GetSystemMetrics(SM_CYSCREEN) - iWindowHeight) / 2;

  // Create the window
  m_hWindow = CreateWindow(m_szWindowClass, m_szTitle,  WS_POPUPWINDOW | WS_CAPTION | WS_MINIMIZEBOX, iXWindowPos, iYWindowPos, iWindowWidth, iWindowHeight, NULL, NULL, m_hInstance, NULL);
  if (!m_hWindow)
    return FALSE;

  // Show and update the window
  ShowWindow(m_hWindow, iCmdShow);
  UpdateWindow(m_hWindow);

  return TRUE;
}

LRESULT GameEngine::HandleEvent(HWND hWindow, UINT msg, WPARAM wParam, LPARAM lParam)
{
  // Route Windows messages to game engine member functions
  switch (msg)
  {
    case WM_CREATE:
      // Set the game window and start the game
      SetWindow(hWindow);
      GameStart(hWindow);
      return 0;

    case WM_SETFOCUS:
      // Activate the game and update the Sleep status
      GameActivate(hWindow);
      SetSleep(FALSE);
      return 0;

    case WM_KILLFOCUS:
      // Deactivate the game and update the Sleep status
      GameDeactivate(hWindow);
      SetSleep(TRUE);
      return 0;

    case WM_PAINT:
      HDC         hDC;
      PAINTSTRUCT ps;
      hDC = BeginPaint(hWindow, &ps);

      // Paint the game
      GamePaint(hDC);

      EndPaint(hWindow, &ps);
      return 0;

    case WM_DESTROY:
      // End the game and exit the application
      GameEnd();
      PostQuitMessage(0);
      return 0;
  }
  return DefWindowProc(hWindow, msg, wParam, lParam);
}

#ifndef GAMEENGINE_H
#define GAMEENGINE_H

#include <windows.h>


//Windows Function Declaration
int WINAPI        WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                     PSTR szCmdLine, int iCmdShow);
LRESULT CALLBACK  WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

//Game Engine Function Declarations
BOOL GameInitialize(HINSTANCE hInstance);
void GameStart(HWND hWindow);
void GameEnd();
void GameActivate(HWND hWindow);
void GameDeactivate(HWND hWindow);
void GamePaint(HDC hDC);
void GameCycle();

//Game Engine Class
class GameEngine
{
   protected:
//Member Variables
     static GameEngine*  m_pGameEngine;
     HINSTANCE           m_hInstance;
     HWND                m_hWindow;
     TCHAR               m_szWindowClass[32];
     TCHAR               m_szTitle[32];
     WORD                m_wIcon, m_wSmallIcon;
     int                 m_iWidth, m_iHeight;
     int                 m_iFrameDelay;
     BOOL                m_bSleep;
     
public:
        //Constructor/Deconstructor
        GameEngine(HINSTANCE hInstance, LPTSTR szWindowClass, LPSTR szTitle,
           WORD wIcon, WORD wSmallIcon, int iWidth = 640, int iHeight = 480);
        virtual ~GameEngine();
        
        //General Methods
        static GameEngine*   GetEngine() { return m_pGameEngine; };
        BOOL                 Initialize(int iCmdShow);
        LRESULT              HandleEvent(HWND hWindow, UINT msg, WPARAM wParam,
                                LPARAM lParam);
                                
        //Accessor Methods
        HINSTANCE    GetInstance()   { return m_hInstance; };
        HWND         GetWindow()     { return m_hWindow; };
        void         SetWindow(HWND hWindow) { m_hWindow = hWindow; };
        LPTSTR       GetTitle()      { return m_szTitle; };
        WORD         GetIcon()       { return m_wIcon; };
        WORD         GetSmallIcon()  { return m_wSmallIcon; };
        int          GetWidth()      { return m_iWidth; };
        int          GetHeight()     { return m_iHeight; };
        int          GetFrameDelay() { return m_iFrameDelay; };
        void         SetFrameRate(int iFrameRate) { m_iFrameDelay = 1000 /
                        iFrameRate; };
        BOOL         GetSleep()      { return m_bSleep; };
        void         SetSleep(BOOL bSleep) { m_bSleep = bSleep; };
};

#endif