brush = CreateSolidBrush(RGB(0, 0, 0));
system_brush = (HBRUSH)SelectObject(hdc, brush);
Rectangle(hdc, x_square_old - 2, y_square_old - 2, x_square_old + 2, y_square_old + 2);
SetPixel(hdc, x_square_old, y_square_old, RGB(100, 100, 100));
SelectObject(hdc, system_brush);
DeleteObject(brush);