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                <button id="top">TOP</button>


                #top {
	position: fixed;
	bottom: 0;
	transform: translateY(100%);
	transition: transform .3s;
#top.view {
	transform: translateY(-2.5vw);

/* 以下特に不要 */

body {
	background: #333;
body::before {
	content: '';
	display: block;
	height: 200vh;
	background: linear-gradient(#c6cca5 20%,#8ab8a8 20% 40%,#6b9997 40% 60%,#54787d 60% 80%,#615145 80%);

#top {
	right: 1em;
	border-radius: .2em;
	border: none;
	background: #fff;
	outline: none;



let topBtn = $('#top');
let topBtnView = false;

	let now = $(window).scrollTop();
	if( topBtnView != now>=window.innerWidth*0.01 ) {
		topBtnView = !topBtnView;