Hover and click on CSS triangle

Question

I have a triangle with a javascript function that moves that image.

The issue is that the element has a square shape so click and hover state are triggered ouside the triangle (see the red part in following image) :

How can I prevent hover and click outside the triangle shape and allow click/hover state only inside the triangle shape?

Answer 1

To prevent hover and click outside the CSS triangle you can use transforms to make the the triangle.

This technique is described here : CSS Triangles with transform rotate

The point is to use a wrapper with hidden overflow and rotate the clickable/hoverable element so that it actualy has a triangular shape and prevent the click event or hover state outside the triangle.

Demo: Click and hover on a CSS triangle

.tr {
  width: 40%;
  padding-bottom: 28.2842712474619%; /* = width / sqrt(2) */
  position: relative;
  overflow: hidden;
}
.tr a {
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background-color: rgba(0, 122, 199, 0.7);
  transform-origin: 0 100%;
  transform: rotate(45deg);
  transition: background-color .3s;
}
/** hover effect **/
.tr a:hover {
  background: rgba(255, 165, 0, 0.7);
}

<div class="tr"><a href="#"></a></div>

---

Another approach would be to use an SVG with a clickable triangle :

#tr{
  fill:transparent;
  transition:fill .3s;
}
#tr:hover{
  fill: orange;
}

/** for the demo **/
html,body{height:100%;margin:0; padding:0;}
body{background:url('https://farm8.staticflickr.com/7435/13629508935_62a5ddf8ec_c.jpg') center no-repeat;background-size:contain;}
svg{display:block;width:30%;margin:0 auto;}

<svg viewbox="-2 -2 104 64">
  <a xlink:href="#">
    <polygon id="tr" points="50 0 100 60 0 60" fill="transparent" stroke="darkorange" stroke-width="2"/>
  </a>
</svg>