.index {
    position: relative;
    height: 100%;
}

.index .left {
    position: absolute;
    width: 220px;
    height: 100%;
    overflow: auto;
    top: 0;
    left: 0;
    background-color: var(--color-light);
}

.index .right {
    margin-left: 235px;
    box-sizing: border-box;
    height: 100%;
}