<!DOCTYPE html>
<html>
<body>
<svg width="300px" height="100px">
    <rect x="0" y="0" width="300" height="100" stroke="black" stroke-width="1" />
    <circle cx="0" cy="50" r="15" fill="blue" stroke="black" stroke-width="1">
        <animate attributeName="cx" from="0" to="100" dur="5s" repeatCount="indefinite" />
    </circle>
</svg>
</body>
</html>