#back-img {
	position: fixed;
	top: 0;
	min-width: 50vw;
	height: 100vh;
	z-index: -100;
	background-color: rgb(0,0,0);
	background-color: var(--bg1);
}

#back-img * {
	position: absolute;
	width: 100%;
	height: 100%;
	background-repeat: no-repeat;
	background-size: cover;
	background-position: 0 0;
	transition: .2s 0s opacity ease-in-out, .4s 0s background-position ease-out;
}

#back-img #bg-desktop {
	opacity: 1;
	background-image: url("../img/back_desktop.jpg");
}
#back-img #bg-mobile {
	opacity: 0;
	background-image: url("../img/back_mobile.jpg");
}

@media only screen and (max-width: 767px) {
	#back-img {
		width: 100vw;
		height: 100vh;
	}
	#back-img #bg-desktop {
		opacity: 0;
	}
	#back-img #bg-mobile {
		opacity: 1;
	}
}