https://sstl.co.uk/js/tickconfig.js?v=feKl7y9-_f6s6AKP7dw9Dl01kXbOXOFOcbnnCCUJ_Uk

1$(document).ready(function () {
2
3    function box() {
4        var winTop = $(window).scrollTop(),
5            winBot = winTop + $(window).height();
6
7        var mostVisible = 0;
8
9        $('.config-boxes').each(function () {
10            var elmOffsetTop = $(this).offset().top - winTop,
11                elmHeight = $(this).height(),
12                elmOffsetBottom = $(this).offset().top + elmHeight - winBot,
13                elmvisible = elmHeight;
14
15            // if this is less than 0 it means the top of the element is above the top of the window, we minus that from the visible var
16            if (elmOffsetTop < 0) {
17                elmvisible = elmHeight + elmOffsetTop;
18            }
19            // if this is greater than 0 it means the bottom of the element is below the bottom of the window, we minus that from the visible var
20            if (elmOffsetBottom > 0) {
21                elmvisible = elmvisible - elmOffsetBottom;
22            }
23            // If we get a negative visible value we set it to 0
24            if (elmvisible < 0) {
25                elmvisible = 0;
26            }
27            // Keep a running total of the most visible, if we beat it update it.
28            if (elmvisible > 0) {
29                $(this).find(".config-wrap").addClass("animate");
30
31            }
32            mostVisible = elmvisible;
33        });
34    }
35    box();
36
37    $(window).scroll(function () {
38        box();
39    });
40});