HWND CreateOverlayWindow(HINSTANCE hInstance, int width, int height) {
    WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_HREDRAW | CS_VREDRAW, WndProc, 0, 0, hInstance, NULL, NULL, NULL, NULL, "OverlayClass", NULL };
    RegisterClassEx(&wc);
    
    HWND hWnd = CreateWindowEx(
        WS_EX_TOPMOST | WS_EX_TRANSPARENT | WS_EX_LAYERED | WS_EX_NOACTIVATE,
        "OverlayClass", "Overlay", WS_POPUP, 0, 0, width, height, NULL, NULL, hInstance, NULL
    );
    
    SetLayeredWindowAttributes(hWnd, RGB(0, 0, 0), 0, LWA_COLORKEY);
    MARGINS margins = { -1, -1, -1, -1 };
    DwmExtendFrameIntoClientArea(hWnd, &margins);
    
    ShowWindow(hWnd, SW_SHOW);
    return hWnd;
}