.sec1 { 
    position: absolute;
    width: 100%; 
    height: 900px;
    left: 50%;
    top:0;
    transform: translateX(-50%);
}
canvas {
    position: absolute;
    top: 0%;
    left: 50%;
    transform: translateX(-50%);
}
#canvas {
    z-index: 3;
}
#canvas_back {
    left: calc(50% - 2px);
}


.line_container {
    width: 100%;
    height: 100%;
}


.line, .line_mid, .line_curve_bot, .line_curve_top {
    width: 3px;
    height: 65px;
    background: #fff;
    opacity: 0.5;

    position: absolute; 
    z-index: 3;
}

.top{
    z-index: 1;
}


.line_curve_bot, .line_curve_top { 
    transform-origin: center -98px;
    /* background: #fff; */
}

@media screen and (max-width: 1920px) {
    .sec1 {
        width: 1920px;
    }
}