track.css

:root {
    --theSize: 0px;

    --relative-unit: calc(var(--theSize) / 645);
    --sliderStart: calc((100% - var(--theSize)) / 2);
    --sliderEnd: calc(50% + (var(--theSize) / 2));
}

#cs3 {
    position: absolute;
    transform: rotate(-90deg) translateX(calc((-1 * var(--theSize) / 2) + 12.5 * var(--relative-unit))) translateY(calc(-1 * var(--theSize) / 2 - 25 * var(--relative-unit)));
}

input[type=range] {
    -webkit-appearance: none;
    height: calc(25 * var(--relative-unit));
    background-image: linear-gradient(to right, black, white);
    outline: none;
    -webkit-transition: .2s;
    transition: opacity .2s;
    border-radius: calc(10 * var(--relative-unit));
    box-shadow: 0px 0px calc(0 * var(--relative-unit)) calc(1 * var(--relative-unit)) rgba(128, 128, 128, 0.33);
}

input[type=range]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: calc(18 * var(--relative-unit));
    height: calc(40 * var(--relative-unit));
    background: #ddd;
    border-radius: calc(4 * var(--relative-unit));
    cursor: pointer;
    background-attachment: fixed, fixed;
    background-clip: padding-box, border-box;
    border: calc(1.5 * var(--relative-unit)) solid rgba(128, 128, 128, 1);
}

input[type=range]::-moz-range-thumb {
    width: calc(18 * var(--relative-unit));
    height: calc(40 * var(--relative-unit));
    background: #ddd;
    border-radius: calc(4 * var(--relative-unit));
    cursor: pointer;
    background-attachment: fixed, fixed;
    background-clip: padding-box, border-box;
    border: calc(1.5 * var(--relative-unit)) solid rgba(128, 128, 128, 1);
}