function ioHandler(entries) {
    for (let entry of entries) {
      entry.target.style.opacity = entry.intersectionRatio.toFixed(2);
      entry.target.addEventListener('click', function(e) {
        if (this.nextElementSibling !== null) {
          this.nextElementSibling.scrollIntoView({
            'behavior': 'smooth'
          });
        }
      },true);

      if (entry.intersectionRatio > .5) {
        entry.target.classList.add('active')
      } else {
        entry.target.classList.remove('active')
      }
    }
  }