<!DOCTYPE html>
<html>
<head>
<style type="text/css">
body
{
background: gray;
}
polygon.hoverable
{
fill: transparent;
stroke: darkgray;
stroke-width: 4;
cursor: pointer;
}
polygon.hoverable:hover
{
stroke:black;
}
</style>
</head>
<body>
<p>Gray initial outline added for visibility. Can replace with 'none'.</p>
<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
<polygon class="hoverable" points="220,100 300,210 170,250"
onclick="alert('I am click functionality!');"/>
</svg>
</body>
</html>