.slider {
    width: 60vw;
    height: 45vw;
    position: relative;
    background: #ccc;
}

.slider__before {
    width: 60vw;
    height: 45vw;
    position: absolute;
    background-position: left;
    background-size: cover;
    z-index: 2;
}

.slider__after {
    width: 60vw;
    height: 45vw;
    position: absolute;
    background-position: center;
    background-size: cover;
}

.slider__resize {
    width: 1px;
    position: absolute;
    height: 100%;
    top: 0;
    right: 0;
    background-color: #fff;
    cursor: ew-resize;
}

.slider__resize:before {
    content: '»';
    position: absolute;
    line-height: 3rem;
    height: 3.25rem;
    font-size: 1.5rem;
    text-align: center;
    top: calc(50% - 2rem);
    left: 0;
	color: #fff;
    background-color: rgba(255, 255, 255, 0.3);
    border-radius: 0 10px 10px 0;
}

.slider__resize:after {
    content: "«";
    position: absolute;
    line-height: 3rem;
    height: 3.25rem;
    font-size: 1.5rem;
    top: calc(50% - 2rem);
    right: 0;
	color: #fff;
    background-color: rgba(255, 255, 255, 0.3);
    border-radius: 10px 0 0 10px;
}