* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100vw;
    height: 100vh;
}

.slider {
    width: 1024px;
    height: 512px;
    position: relative;
    background: lightgray;
}

.slider__before {
    width: 1024px;
    height: 512px;
    position: absolute;
    z-index: 2;
    background: no-repeat center center fixed;
    background-size: cover;
}

.slider__after {
    width: 1024px;
    height: 512px;
    position: absolute;
    background: no-repeat center center fixed;
    background-size: cover;
}

.slider__resize {
    width: 5px;
    position: absolute;
    height: 100%;
    top: 0;
    right: 0;
    background-color: black;
    cursor: e-resize;
}

.slider__resize:before {
    content: '>';
    position: absolute;
    font-size: 30px;
    font-weight: bold;
    top: 50%;
    left: 0;
}

.slider__resize:after {
    content: "<";
    position: absolute;
    font-size: 30px;
    font-weight: bold;
    top: 50%;
    right: 0;
}