#start_game, #index_login_html, #start_html
{
    background-image: url('/loading_screen.jpg');
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-size: cover;
    background-position: center;
    height: 100%;
}

#flex_main, #container_main
{
    height: 100%;
}

#container_main
{
    padding-left: 0;
    padding-right: 0;
}

#s_game_btn
{
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
}