SOURCE

const rows = document.querySelectorAll('#ui ul li')
const html = document.documentElement

document.addEventListener('scroll', (e) => {
  let scrolled = html.scrollTop / (html.scrollHeight - html.clientHeight)
  
  let total =  1 / rows.length
  
  for (let [index, row] of rows.entries()) {
    let start = total * index
    let end = total * (index + 1)
    
    let progress = (scrolled - start) / (end - start)
    if (progress >= 1) progress = 1
    if (progress <= 0) progress = 0
    
    row.style.setProperty('--progress', progress)
  }
})

<h2>
  Superfast wireless
  <p>Hello 5G.</p>
</h2>

<div id="iphone">
  <div id="hardware"></div>
  <div id="ui">
    <img src="https://assets.codepen.io/2002878/iphone12-5g_top_ui.jpg" class="top-ui" alt="">
    
    <ul>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_01.jpg" />
      </li>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_02.jpg" />
      </li>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_03.jpg" />
      </li>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_04.jpg" />
      </li>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_05.jpg" />
      </li>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_06.jpg" />
      </li>
      <li>
        <img src="https://assets.codepen.io/2002878/iphone12-5g_show_07.jpg" />
      </li>
    </ul>
  </div>
</div>

:root {
  --device-width: 770px;
  --device-height: 1336px;
  --ui-width: 640px;
  font-size: 15px;
}

body {
  background-color: #000;
  margin: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  font-family: Helvetica;
  padding: 4rem 0;
}

h2 {
  color: #6e6e73;
  text-align: center;
  font-size: 4.5rem;
  font-weight: 600;
  margin: 6rem 0;
}

h2 p {
  margin: 0;
  color: #fff;
}

#iphone {
  position: relative;
  width: var(--device-width);
  height: var(--device-height);
}

#hardware {
  width: 100%;
  height: 100%;
  background-image: url(https://assets.codepen.io/2002878/iphone12-5g_on_phone.jpg);
  background-size: var(--device-width) var(--device-height);
  
  mask-image: url(https://assets.codepen.io/2002878/iphone12-5g_on_phone_mask.png);
  -webkit-mask-image: url(https://assets.codepen.io/2002878/iphone12-5g_on_phone_mask.png);
  
  mask-size: var(--device-width) var(--device-height);
  -webkit-mask-size: var(--device-width) var(--device-height);
  
}

#ui {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
}

#ui .top-ui {
  display: block;
  width: var(--ui-width);
  height: auto;
  margin: 70px auto 0;
  padding-bottom: 30px;
  border-bottom: 1px solid #222;
}

#ui ul {
  list-style: none;
  margin: 0;
  padding: 0;
  
  --progress: 0;
}

#ui ul li img {
  display: block;
  width: var(--ui-width);
  height: auto;
  margin: 10px auto;
  padding-bottom: 10px;
  border-bottom: 1px solid #222;
  transform: scale(calc(1.8 - (0.8 * var(--progress)))) translateY(calc(-60px * (1 - var(--progress))));
  opacity: var(--progress);
}