if (border_fade_out)
{
    if (border_alpha > 0)
    {
        border_alpha -= border_fade_value;
        if (border_alpha <= 0)
            border_alpha = 0;
    }
}
else if (border_fade_in)
{
    if (border_alpha <= 1)
    {
        border_alpha += border_fade_value;
        if (border_alpha >= 1)
            border_alpha = 1;
    }
}