javascript - jQuery 'click' event not firing -

i can't life of me figure out why click function isn't working on codepen. know how use jquery's click method. if second set of eyes @ , diagnose, appreciated. here fork of codepen, click method top , looks this:

$('button').click(function() {   alert('clicked!'); }); 

here relevant html:

<section class="left">   <button class="left-button">show chart</button> </section> 

here codepen.

(i've used exact same click method here , works fine)

it's css. removed css , worked. buttons blocked stuff. need in front clicked.

your sections set z-index of -1.