function handleSticky() {
  if (window.scrollY >= window.innerHeight * 0.65) {
    document.querySelector('header').setAttribute('data-header-visible', true);
  } else {
    document.querySelector('header').setAttribute('data-header-visible', false);
  }
  if (document.querySelector('.intro')) {
    const intro = document.querySelector('.intro');
    intro.style = `--percentIntroScroll : ${window.scrollY / intro.offsetTop - 0.2}`;
  }
  if (document.querySelector('.features')) {
    const features = document.querySelector('.features');
    features.style = `--percentFeatureScroll : ${window.scrollY / features.offsetTop - 0.4}`;
  }
}
window.onload = function () {
  window.addEventListener('scroll', this.handleSticky);
};