Винапи с++, суть программы в том, что компьютер угадывает число пользователя. Нужна доработка кода

#include <windows.h>
#include <tchar.h>
#define  APPNAME    _T("LabWork1")
#define  APPCLS     _T("Nuklon")
#define  IDC_SMALL  100
#define  IDC_BIG    101
#define  IDC_ANSWER 102
#define  _creatButton(name, id, x, y) \
CreateWindow(_T("BUTTON"), name, WS_CHILD | BS_USERBUTTON | WS_VISIBLE,\
x, y, 200, 60, hwnd, (HMENU)id, (HINSTANCE)lParam, NULL)
//////////////////////////////////////////////////////////
LRESULT CALLBACK  _wndProc(HWND, UINT, WPARAM, LPARAM);
int   _creatWindow(HINSTANCE, const TCHAR*);
void  _helloDlg(HWND, int, int);
void  _answerCPU(HWND, int, int, char);
/// /////////////////////////////////////////////////////
int  f_n = 1;
int  l_n = 1000;
//////////////////////////////////////////////////////////
int WINAPI  _tWinMain(HINSTANCE hInstance, HINSTANCE, LPTSTR, int) { return _creatWindow(hInstance, _T("LabWork1. Less or more?"));}
///////////////////////ОКНО//////////////////////
int  _creatWindow(HINSTANCE hInst, const TCHAR* caption) {
    HWND hwnd = NULL;
    MSG  msg = { 0 };
    WNDCLASS ofs = {
          0, _wndProc, 0, 0,  hInst, 0, LoadCursor(NULL, IDC_ARROW),
         (HBRUSH)(COLOR_WINDOW + 2), 0, APPCLS };
    if (!RegisterClass(&ofs))
        return 1;
    hwnd = CreateWindow(APPCLS, caption, WS_OVERLAPPEDWINDOW & ~WS_SIZEBOX,
        CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, HWND_DESKTOP,
        NULL, hInst, hInst);
    if (hwnd == NULL) {
        UnregisterClass(APPCLS, hInst);
        return 1;}
    ShowWindow(hwnd, SW_SHOW);
    UpdateWindow(hwnd);
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);}
    return 0;}
////////////////////////////////////////////////////////
LRESULT CALLBACK _wndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    static HWND bbig = NULL;
    static HWND bsmall = NULL;
    RECT  rc;
    switch (msg) {
    case WM_CREATE:
        GetClientRect(hwnd, &rc);
        bsmall = _creatButton(_T("МЕНЬШЕ"), IDC_SMALL, rc.right / 10 + 350, rc.bottom / 2 + 30);
        bbig = _creatButton(_T("БОЛЬШЕ"), IDC_BIG, rc.right / 10 + 350, rc.bottom / 2 - 40);
        SendMessage(hwnd, WM_COMMAND, MAKEWPARAM(IDC_ANSWER, 0), 0);
        break;
    case WM_COMMAND:
        switch (LOWORD(wParam)) {
        case IDC_SMALL:
            _answerCPU(hwnd, f_n, l_n, '<');
            break;
        case IDC_BIG:
            _answerCPU(hwnd, f_n, l_n, '>');
            break;
        case IDC_ANSWER:  
            _helloDlg(hwnd, f_n, l_n);
            _answerCPU(hwnd, f_n, l_n, 0);
            break;
        }
        break;
    case WM_DESTROY:
        DestroyWindow(bsmall);
        DestroyWindow(bbig);
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);}
    return 0;}
////////////////////НАЧАЛО/////////////////////////////////
void  _helloDlg(HWND hwnd, int f, int l) {
    TCHAR buf[64];
    wsprintf(buf, _T("Для начала игры задумайте число от %d до %d"), f, l);
    MessageBox(hwnd, buf, APPNAME, MB_OK | MB_ICONINFORMATION);
}
///////////////////////////////////////////////////////
void  _answerCPU(HWND hwnd, int _f, int _l, char ch) {
    static int f = _f;
    static int l = _l;
    static int num = 0;
    TCHAR buf[64];
    int   id;
 
    switch (ch) {
    case '<':  // МЕНЬШЕ
        l = num;
        break;
    case '>':  // БОЛЬШЕ
        f = num + 1;
        break;
    }
    num = (f + l) / 2; 
 
    wsprintf(buf, _T("Загаданным числом является %d. Да/Нет?"), num);
    id = MessageBox(hwnd, buf, APPNAME, MB_YESNO | MB_ICONQUESTION);
    if (id != IDYES)
        return;
    
 
    wsprintf(buf, _T("Получилось! Ваше число %d"), num);
 
    id = MessageBox(hwnd, buf, APPNAME, MB_OKCANCEL | MB_ICONINFORMATION);
    if (id == IDCANCEL) 
        SendMessage(hwnd, WM_DESTROY, 0, 0);
    else { 
        f = _f;
        l = _l;
        SendMessage(hwnd, WM_COMMAND, MAKEWPARAM(IDC_ANSWER, 0), 0);
    }
}

if (f == l) {
    MessageBox(hwnd, "Вы обманываете", APPNAME, MB_OK | MB_ICONEXCLAMATION);
    SendMessage(hwnd, WM_DESTROY, 0, 0);
}
switch (ch) {
...