</head>
<body>
<canvas style="position: fixed; top: 0px; left: 0px"></canvas>
+ <div style="position: fixed; bottom: 0px; left: 0px">
+ <input type="checkbox" id="grid"><label for="grid">Show grid</label><br>
+ <input type="checkbox" id="lines"><label for="lines">Show lines</label><br>
+ <input type="checkbox" id="circles"><label for="circles">Show circles</label><br>
+ </div>
</body>
</html>