* {
    margin: 0;
    padding: 0;
    user-select: none;
    box-sizing: border-box;
}

body {
    height: 300vh;
    background: url(img/bg.jpg);
    background-size: cover !important;
    background-attachment: fixed !important;
}

section {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100vh;
}

section .side {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

section .side#side1 {
    background: black;
    clip-path: polygon(0 100%, 0 0, 0 0, 38% 39%, 38% 64%, 0 100%);
}

section .side#side2 {
    background: white;
    clip-path: polygon(100% 100%, 100% 0, 0 0, 38% 39%, 38% 64%, 0 100%);
    border-top: green 285px solid;
    border-bottom: red 265px solid;
}

@media screen and (min-width: 300px) and (max-width: 800px)  {
    body {
        background: url(img/bg2.jpg);
    }
}