页面右侧和左侧的三角形

Question

想要将按钮对齐到屏幕的右侧和左侧，当用户滚动（定位为绝对或固定）时保留按钮，然后在屏幕缩小时相对定位。

重大问题我希望白色三角形（背景）中的文字/图标指向内部。

到目前为止......

<div id="bnav">
    <?php bnNav_content_nav( 'nav-below' ); ?>
</div>

CSS

[class*="navigation"] .nav-previous, 
[class*="navigation"] .nav-next { 
  position: fixed;
  z-index: 999;
  top: 50%; bottom: 0;
  transform: translateY(-30px);
}

[class*="navigation"] .nav-previous { left: 0px; }
[class*="navigation"] .nav-next { right: 0px; } 

[class*="navigation"] .nav-previous a,
[class*="navigation"] .nav-next a {
  display: block;
  font-size: 1.75em; 
  color: #fff;
  background-color: #1b1b1b;
  text-align: center;
  padding: 10px;
  transition: background-color 0.35s ease; 
  -webkit-transition: background-color 0.35s ease;
  -moz-transition: background-color 0.35s ease;
  -ms-transition: background-color 0.35s ease;
  -o-transition: background-color 0.35s ease;
}

文本是通过wordpress动态创建的，并放入div标记为.nav-next和.nav-previous