Не создается кнопка в WM_CREATE

#include <Windows.h>
 
#define BUTTON_ONE 3000
 
ATOM RegClass(WNDCLASSEX*);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
 
HINSTANCE hInstance;
HWND hWnd;
LPCTSTR headerName = L"Калькулятор";
LPCTSTR className = L"calculate";
const int buttonWidth = 30, buttonHeight = 30;
 
int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, LPSTR lpCmdLine, int nCmdShow)
{
    int cx, cy, xPos, yPos;
    int width = 200, height = 300;
    WNDCLASSEX wc;
    MSG msg;
 
    cx = GetSystemMetrics(SM_CXSCREEN);
    cy = GetSystemMetrics(SM_CYSCREEN);
    xPos = cx / 2 - width / 2;
    yPos = cy / 2 - height / 2;
    
    if(!RegClass(&wc))
    {
        MessageBox(NULL, L"Error RegClass()", L"Error", MB_OK);
        return 0;
    }
    
    hWnd = CreateWindowEx(0, className, headerName, WS_OVERLAPPEDWINDOW | WS_VISIBLE, xPos, yPos, width, height, NULL, NULL, hInstance, NULL);
    if(!hWnd)
    {
        MessageBox(NULL, L"Error CreateWindowEx()", L"Error", MB_OK);
        return 0;
    }
 
    ShowWindow(hWnd, SW_SHOW);
    UpdateWindow(hWnd);
 
    while(GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    DestroyWindow(hWnd);
    UnregisterClass(className, hInstance);
    
    return 0;
}
ATOM RegClass(WNDCLASSEX *wc)
{
    wc->cbClsExtra = 0;
    wc->cbWndExtra = 0;
    wc->cbSize = sizeof(WNDCLASSEX);
    wc->style = CS_HREDRAW | CS_VREDRAW;
    wc->lpszClassName = className;
    wc->lpszMenuName = NULL;
    wc->hInstance = hInstance;
    wc->lpfnWndProc = WndProc;
    wc->hCursor = LoadCursor(NULL, IDC_ARROW);
    wc->hIcon = LoadIcon(NULL, IDI_WINLOGO);
    wc->hIconSm = wc->hIcon;
    wc->hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
 
    return RegisterClassEx(wc);
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    static HWND button;
    switch(msg)
    {
    case WM_CREATE:
        button = CreateWindow(L"BUTTON", L"1", WS_VISIBLE | WS_CHILD | BS_CENTER, 20, 20, buttonWidth, buttonHeight, hWnd, (HMENU)BUTTON_ONE, hInstance, NULL);
        return 0;
 
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    case WM_CLOSE:
        PostQuitMessage(0);
        return 0;
 
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }
}