<div id="smooth-wrapper">
  <div id="smooth-content">
    <header class="header">
      <h1 class="title">ScrollSmoother</h1>
      <button class="button">Jump to C</button>
    </header>
    <div class="box box-a" data-speed="clamp(0.5)">a</div>
    <div class="box box-b" data-speed="clamp(0.8)">b</div>
    <div class="box box-c" data-speed="1.5">c</div>
    <div class="line"></div>
  </div>
</div>

:root {
	--dark: #1d1d1d;
  --grey-dark: #414141;
	--light: #fff;
	--mid: #ededed;
  --grey: #989898;
  --gray: #989898;
	--green: #28a92b;
  --green-dark: #4e9815;
	--green-light: #6fb936;
	--blue: #2c7ad2;
	--purple: #8d3dae;
	--red: #c82736;
	--orange: #e77614;
  accent-color: var(--green);
}
body {
  background-color: #111;
  font-family: "Signika Negative", sans-serif, Arial;
  overscroll-behavior: none;
  margin: 0;
  padding: 0;
  overflow-x: hidden;
}

.header {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
}


#smooth-content {
  overflow: visible;
  width: 100%;
  /* set a height because the contents are position: absolute, thus natively there's no height */
  height: 4000px;

  background-image:
    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;
}

button {
  position: relative; 
}

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

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

.box-b {
  top: 600px;
}

.box-c {
  top: 1000px;
  background-color: #e26c16;
  will-change: transform;
}

.line {
  visibility: hidden;
  width: 2px;
  height: 4000px;
  position: absolute;
  left: 400px;
  top: 0px;
  background-color: #777;
}

header .name {
  color: white;
}

.title {
  text-align: center;
  color: white;
  font-weight: 400;
  font-size: 40px;
}
footer {
  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);
}

.end {
  position: absolute;
  /*   bottom: 0; */
  top: 2400px;
  transform: translateY(-100%);
  font-size: 30px;
  color: white;
}

/* button:not('.box') { breaking for some reason in codepen? */
button {
	display: inline-block;
	outline: none;
	border: none;
	padding: 8px 14px;
	background: var(--light);
  background-image: linear-gradient(to bottom, hsl(0deg 0% 100%), hsl(0deg 0% 94%));
	-webkit-box-shadow: 0px 1px 0px #414141;
	-moz-box-shadow: 0px 1px 0px #414141;
	box-shadow: 0px 1px 0px #414141;
	color: var(--dark);
	text-decoration: none;
	-webkit-border-radius: 4;
	-moz-border-radius: 4;
	border-radius: 4px;
	padding: 12px 25px;
	font-family: "Signika Negative", sans-serif;
	text-transform: uppercase;
	font-weight: 600;
	cursor: pointer;
	line-height: 18px;
}

.light button {
    color: var(--light);
  	background-image: linear-gradient(to bottom, #575757, #414141);
}

button:hover {
	background: var(--green-light);
	background-image: linear-gradient(to bottom, #57a818, #4d9916);
	-webkit-box-shadow: 0px 1px 0px fefefe;
	-moz-box-shadow: 0px 1px 0px fefefe;
	box-shadow: 0px 1px 0px fefefe;
	color: #ffffff;
	text-decoration: none;
}

gsap.registerPlugin(ScrollTrigger, ScrollSmoother);

ScrollTrigger.normalizeScroll(true)

// create the smooth scroller FIRST!
let smoother = ScrollSmoother.create({
  smooth: 2,
  effects: true,
  normalizeScroll: true
});

// pin box-c when it reaches the center of the viewport, for 300px
ScrollTrigger.create({
  trigger: ".box-c",
  pin: true,
  start: "center center",
  end: "+=300",
  markers: true
});

document.querySelector("button").addEventListener("click", e => {
  // scroll to the spot where .box-c is in the center.
  // parameters: element, smooth, position
  smoother.scrollTo(".box-c", true, "center center");
  
  // or you could animate the scrollTop:
  // gsap.to(smoother, {
  // 	scrollTop: smoother.offset(".box-c", "center center"),
  // 	duration: 1
  // });
});