.scan-line {
    pointer-events: none;
    position: fixed;
    top: -100%;
    left: 0;
    width: 100%;
    height: 24px;
    background: linear-gradient(
        to bottom,
        rgba(255, 255, 255, 0) 0%,
        rgba(255, 255, 255, 0.15) 50%,
        rgba(255, 255, 255, 0) 100%
    );
    z-index: 1000;
    animation: scanMove var(--scan-speed, 6s) linear infinite;
}

@keyframes scanMove {
    from { top: -100px; }
    to { top: 100%; }
}