.parallax {
    background-attachment: fixed;
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
}
.parallax-opacity50 {
    opacity: 0.5;
}
.parallax-opacity75 {
    opacity: 0.75;
}
.parallax-opacity25 {
    opacity: 0.25;
}
.parallax-h100 {
    min-height: 100px;
}
.parallax-darken50 {
    background-color: rgba(0, 0, 0, .50);
    background-blend-mode: darken;
}

.parallax-whiten50 {
    background-color: rgba(255, 255, 255, .50);
    background-blend-mode: luminosity;
}