static/css/particles.css

#particles-js {
    position: fixed;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: -1;
    background: linear-gradient(135deg, #ffffff 0%, #f0f4ff 100%);
}

.container {
    position: relative;
    z-index: 1;
}