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                <div id="viewport">
  <div id="content"> 
    <div class="box box-a">a</div>
    <div class="box box-b">b</div>
    <div class="box box-c">c</div> 



                body {
  background-color: #111;
  font-family: "Signika Negative", sans-serif, Arial;

#viewport {
  overflow: hidden;
  position: fixed;
  height: 100%;
  width: 100%;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;

#content {
  overflow: visible;
  width: 100%;
  /* set a height because the contents are position: absolute, thus natively there's no height */
  height: 2400px;
    linear-gradient(rgba(255,255,255,.07) 2px, transparent 2px),
    linear-gradient(90deg, rgba(255,255,255,.07) 2px, transparent 2px),
    linear-gradient(rgba(255,255,255,.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.06) 1px, transparent 1px);
  background-size: 100px 100px, 100px 100px, 20px 20px, 20px 20px;
  background-position: -2px -2px, -2px -2px, -1px -1px, -1px -1px;

.box {
  width: 100px;
  height: 100px;
  background-color: #28a92b;
  position: absolute;
  left: calc(50% - 50px);
  z-index: 100;
  line-height: 100px;
  font-size: 50px;
  text-align: center;
} {
  background-color: red;

.box-a {
  top: 200px;
  background-color: #8d3dae;

.box-b {
  top: 600px;

.box-c {
  top: 1000px;
  background-color: #e26c16;

.line {
  visibility: hidden;
  width: 2px;
  height: 3000px;
  position: absolute;
  left: 400px;
  top: 0px;
  background-color: #777;

header .name {
  color: white;

.title {
  position: absolute;
  width: 100%;
  text-align: center;
  color: white;
  font-weight: 400;
  font-size: 40px;
header {
  position: fixed;
  right: 0px;
  bottom: 0px;
  padding: 6px 10px 10px 12px;
  border-top-left-radius: 26px;
  z-index: 100;
  background-color: rgba(0,0,0,0.5);



// you must wrap your content <div> in another <div> that will serve as the viewport


// this is the helper function that sets it all up. Pass in the content <div> and then the wrapping viewport <div> (can be the elements or selector text). It also sets the default "scroller" to the content so you don't have to do that on all your ScrollTriggers.
function smoothScroll(content, viewport, smoothness) {
	content = gsap.utils.toArray(content)[0];

	gsap.set(viewport || content.parentNode, {overflow: "hidden", position: "fixed", height: "100%", width: "100%", top: 0, left: 0, right: 0, bottom: 0});
  gsap.set(content, {overflow: "visible", width: "100%"});
	let getProp = gsap.getProperty(content),
		//setProp = value => window.scrollTo(0, Math.abs(value) ), 
		setProp = gsap.quickSetter(content, "y", "px"),
    removeScroll = () => = "visible",

	function onResize() {
		height = content.clientHeight; = "visible" = height + "px";
  ScrollTrigger.addEventListener("refreshInit", onResize);
  ScrollTrigger.addEventListener("refresh", () => {
  ScrollTrigger.defaults({scroller: content});

	ScrollTrigger.prototype.update = p => p; // works around an issue in ScrollTrigger 3.6.1 and earlier (fixed in 3.6.2, so this line could be deleted if you're using 3.6.2 or later)

	ScrollTrigger.scrollerProxy(content, {
		scrollTop(value) {
			return arguments.length ? setProp(-value) : -getProp("y");
		getBoundingClientRect() {
			return {top: 0, left: 0, width: window.innerWidth, height: window.innerHeight};

	gsap.fromTo(content, {y:0}, {
		y: () => document.documentElement.clientHeight - height,
		ease: "none",
		onUpdate: ScrollTrigger.update,
		scrollTrigger: {
      scroller: window,
			invalidateOnRefresh: true,
			start: 0,
			end: () => height - document.documentElement.clientHeight,
			scrub: smoothness || 1,
			onRefresh: self => {
				// when the screen resizes, we just want the animation to immediately go to the appropriate spot rather than animating there, so basically kill the scrub. 
  let snapSections =  gsap.utils.toArray('.box'),
  ScrollTrigger.create( {
		trigger: snapSections[0], // first section
    scroller: '#content',
    start: 'top bottom',
    endTrigger: snapSections[snapSections.length - 1], // last section
    end: 'bottom top',
    onRefresh: self => {
      // translate the offsetTop of each section into a progress value between the ScrollTrigger's start and end for snapping
      let values = =>
                                     gsap.utils.normalize(self.start, self.end,  section.offsetTop)
      values.push(1) // make sure it can snap to the end of the last section.
      snapper =  gsap.utils.snap(values) // create a function that'll do the snapping for us. Just pass in a value and it'll return the closest one in the Array.
    snap: value => snapper(value),