<style>
    html, body {
        margin: 0;
        padding: 0;
    }
    rect {
        fill: none;
        stroke-width: 6;
        stroke-linejoin: round;
        stroke: green;
        width: 100px;
        height: 100px;
    }
</style>
<body>
    <svg>
        <rect x="30" y="30"/>
    </svg>
</body>