<html>
<head>
    <style>
        .container {
            width: 400px;
            height: 400px;
            clip-path: inset(10px 250px 250px 10px);
        }
        canvas {
            box-sizing: border-box;
            width: 100%;
            height: 100%;
            border-radius: 50%;
            padding: 120px;
            border: 13px solid green;
            background-color: cyan;
        }
    </style>
    <script>
        function redraw()
        {
            var canvas = document.getElementsByTagName('canvas')[0];
            let context = canvas.getContext("webgl");
            context.viewport(0, 0, context.drawingBufferWidth, context.drawingBufferHeight);
            context.clearColor(1, 0, 0, 1);
            context.clear(context.COLOR_BUFFER_BIT | context.DEPTH_BUFFER_BIT);
        }

        window.addEventListener('load', () => {
            redraw();
        }, false);
    </script>
</head>
<body>
    <div class="container">
        <canvas></canvas>
    </div>
</body>
</html>