.flat-slider {
    -webkit-appearance: none;
    width: 100%;
    height: 10px;
    margin: 5px 0;
    border-radius: 5px;
    background: #dddddd;
    outline: none;
    opacity: 0.7;
    -webkit-transition: .2s;
    transition: opacity .2s;
}

.flat-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 15px;
    height: 15px;
    border-radius: 50%;
    border: 1px solid #666666;
    background: #ffffff;
    cursor: pointer;
}

.flat-slider::-moz-range-thumb {
    width: 25px;
    height: 25px;
    border-radius: 50%;
    border: 1px solid #666666;
    background: #ffffff;
    cursor: pointer;
}