text: $(window).on('scroll', function() {
      const windowHeight = $(window).height()
      const scrollValue = $(this).scrollTop()
  
      const $art2 = $('.art2');
      const art2FromTop = $art2.offset().top;
      const art2Height = $art2.outerHeight();
  
      const $art3 = $('.art3');
      const art3FromTop = $art3.offset().top;
      const art3Height = $art3.outerHeight();
  
      const $art4 = $('.art4');
      const art4FromTop = $art4.offset().top;
      const art4Height = $art4.outerHeight();
  
      if (scrollValue > art2FromTop + art2Height - windowHeight) {
          $art2.addClass('active');
      }
  
      if (scrollValue > art3FromTop + art3Height - windowHeight) {
          $art3.addClass('active');
      }
  
      if (scrollValue > art4FromTop + art4Height - windowHeight) {
          $art4.addClass('active');
      }
  
      if (scrollValue < 100) {
          $('article').removeClass('active');
      }
  
      // Druga sekcja
      const $op1 = $('.op1');
      const op1FromTop = $op1.offset().top;
      const op1Height = $op1.height();
  
      const $op2 = $('.op2');
      const op2FromTop = $op2.offset().top;
      const op2Height = $op2.height();
  
      if (scrollValue > op1FromTop + op1Height / 2 - windowHeight) {
          $op1.addClass('active');
      }
  
      if (scrollValue > op2FromTop + op2Height / 2 - windowHeight) {
          $op2.addClass('active');
      }
  })