title: Css invert background color
body: <p>At the moment my css looks like this:</p>
  
  <p><a href="https://i.stack.imgur.com/Ew0c6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ew0c6.png" alt="enter image description here"></a></p>
  
  <p>But I want the inverse of the green border-radius blocks, I want this:</p>
  
  <p><a href="https://i.stack.imgur.com/uflsV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uflsV.png" alt="enter image description here"></a></p>
  
  <p>Any idea how to achieve this with the least amount of extra divs and stuff? Here is my code so far:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.navbar {
    background-color: blue;
    height: 35px;
  }
  
  button {
    color: white;
    border: none;
    // background-color: green;
    background-color: transparent;
    height: 100%;
    padding: 0px 10px;
    cursor: pointer;
  }
  
  button.selected {
    background-color: white;
    color: black;
    cursor: default;
    border-radius: 15px 15px 0px 0px;
    position: relative;
    height: 30px;
    vertical-align: bottom;
  }
  
  button:after,
  button:before {
    background-color: rgb(188, 218, 188);
    height: 20px;
    width: 20px;
    position: absolute;
    content: '';
    bottom: 0px;
  }
  
  button:after {
    right: -20px;
    border-bottom-left-radius: 15px;
  }
  
  button:before {
    left: -20px;
    border-bottom-right-radius: 15px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="navbar"&gt;
    &lt;button&gt;tab1&lt;/button&gt;
    &lt;button&gt;tab2&lt;/button&gt;
    &lt;button class="selected"&gt;tab3&lt;/button&gt;
    &lt;button&gt;tab4&lt;/button&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>