Use the :hover selector to add hover effect. To give a rounded effect, use the border-radius property. You can try to run the following code to set rounded active and hover button with CSS:
Example
<!DOCTYPE html>
<html>
<head>
<style>
.demo {
display: inline-block;
}
.demo a {
color: red;
padding: 5px 12px;
text-decoration: none;
border-radius: 5px;
}
.demo a.active {
background-color: orange;
color: white;
border-radius: 5px;
}
.demo a:hover:not(.active) {
background-color: yellow;
}
</style>
</head>
<body>
<h2>Our Quizzes</h2>
<div class = "demo">
<a href = "prev.html"><</a>
<a href = "quiz1.html">Quiz1</a>
<a href = "quiz2.html">Quiz2</a>
<a href = "quiz3.html">Quiz3</a>
<a href = "quiz4.html" class = "active">Quiz4</a>
<a href = "next.html">></a>
</div>
</body>
</html>