/* Full-page ambient glow */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: -1;

    background:
        /* Top glow */
        radial-gradient(
            ellipse at top,
            rgba(255,255,255,0.25),
            rgba(0,0,0,0.65) 70%
        ),

        /* Bottom glow */
        radial-gradient(
            ellipse at bottom,
            rgba(255,255,255,0.25),
            rgba(0,0,0,0.65) 70%
        ),

        /* Left glow */
        radial-gradient(
            ellipse at left,
            rgba(255,255,255,0.35),
            rgba(0,0,0,0.75) 70%
        ),

        /* Right glow */
        radial-gradient(
            ellipse at right,
            rgba(255,255,255,0.35),
            rgba(0,0,0,0.75) 70%
        );

    background-blend-mode: screen;
}