.parallax-up, .parallax-down {
    opacity: 0;
    transform: translateY(0);
    transition: opacity 1.2s ease, transform 1.2s ease;
    will-change: transform;
}
.parallax-up { transform: translateY(100px); }
.parallax-down { transform: translateY(-100px); }
.parallax-up.visible, .parallax-down.visible {
    opacity: 1;
    transform: translateY(0);
}