title: Hover effect not working on positioned Anchor Tag <a>
body: <p>When I position the element above an image Hover effect stop working. 
  Any idea why? Im learning.</p>
  
  <p>I have some positioned elements, an overlay with opacity on top of a div with a background image in fixed position.</p>
  
  <p>Code entire section and entire CSS :</p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div class="wrapper"&gt; &lt;!-- Global Wrapper --&gt;
  &lt;section&gt;
      &lt;div class="first-row"&gt;
         &lt;div class="first-row__overlay"&gt;
         &lt;/div&gt;
          &lt;div class="jumbotron"&gt;
              &lt;h2 class="jumbotron__header"&gt;This is the Title&lt;/h2&gt;
              &lt;p class="jumbotron__text"&gt;Lorem text
              &lt;/p&gt;
              &lt;div class="under-line"&gt;&lt;/div&gt;
          &lt;/div&gt;
          &lt;a href="#" class="my-Btn"&gt;START NOW&lt;/a&gt;
      &lt;/div&gt;
  &lt;/section&gt;
  </code></pre>
  
  <p>CSS: </p>
  
  <pre><code>* {
    margin: 0;
    padding: 0;
    font-family: 'Arsenal', sans-serif;
    }
  .wrapper {
    margin: 0;
    padding: 0;
    }
  .first-row {
    width: 100%;
    height: 100vh;
    background: url("../images/paradise-1.jpg") no-repeat fixed center center;
    background-size: cover;
    text-align: center;
    position: relative;
    top: 0;
    left: 0;
    z-index: -100;
    }
  .first-row__overlay {
    background-color: rgba(33, 46, 63, 1);
    width: 100%;
    height: 100vh;
    opacity: .35;
    position: relative;
    top: 0;
    left: 0;
    z-index: -99;
    }
  .jumbotron { 
    width: 50%;
    margin: auto;
    color: white;
    position: relative;
    top: -70vh;
    z-index: 1;
    background-color: rgba(0, 0, 0, 0.3);
    }
  .under-line {
    height: 10px;
    width: 0;
    margin: auto;
    background-color: transparent;
    border-bottom: 1px solid white;
    transition: 7s ease;
   }
  .my-Btn {
   position: relative;
    top: -67vh;
    z-index: 99999999;
    color: #1d1e1f;
    font-weight: 300;
    font-size: 1.2em;
    padding: 10px 60px;
    background-color: #fdfdfe;
    border-radius: 30px;
    }
  .my-Btn:hover {
    cursor: pointer;
    }
  </code></pre>