Dúvida no Ex. 7 da Aula 6 - Gradientes

Não consigo gerar o efeito desejado no exercício. Tentei usando o exemplo do próprio exercício mas mesmo assim não consigo o efeito desejado. No meu footer simplesmente não aparece nada ...

bio.css

footer {
    background-color: (0, 0, 0, .3);
    font-family: "Shadows Into Light", sans-serif;
    color: #000;
    padding: 1.5rem;
    clear: both;
    position: fixed;
    width: 100%;
    bottom: 0;
    left: 0;
    box-sizing: border-box;
    height: 1rem;
    -webkit-background-image: radial-gradient(ellipse at left bottom, rgba (60,29,61,0.8), rgba (60,29,61,0.8) 65%, black 65%, black 70%, transparent 70%, transparent);
    -webkit-background-size:  25% 100%;
    -webkit-background-repeat: no-repeat;
    background-image: radial-gradient(ellipse at left bottom,
        rgba (60,29,61,0.8),
        rgba (60,29,61,0.8) 65%,
        black 65%,
        black 70%,
        transparent 70%,
        transparent);
    background-size:  25% 100%;
    background-repeat: no-repeat;
}

site.css

footer {
    background-color: (0, 0, 0, .3);
    font-family: "Shadows Into Light", sans-serif;
    padding: 20px;
    clear: both;
    position: fixed;
    width: 100%;
    bottom: 0;
    left: 0;
    box-sizing: border-box;
    height: 10px;
    /*opacity: 0.3;*/
    background-image: radial-gradient(ellipse at left bottom, rgba (60,29,61,0.8), rgba (60,29,61,0.8) 65%, black 65%, black 70%, transparent 70%, transparent);
    background-size:  25% 100%;
    background-repeat: no-repeat;
}