The engine renders into a HTML5 <canvas> element contained within a <div> element. There are some important considerations when creating the canvas & div: both the canvas and div must have absolutely no border, or mouse coordinate calculations will be incorrect they will be automatically resized by the engine to match the size of your stack, so don't attempt to set their size using HTML or CSS the canvas should be the only element within the containing div, which may be used to hold additional elements as native layers are added to the app. the canvas needs to be easily uniquely identifiable, so that the engine can find it. The absolute minimum canvas element would look something like this:
<div><canvas style="border: 0px none;" id="canvas" oncontextmenu="event.preventDefault();"></canvas></div>
By default, most web browsers will indicate when the canvas has focus by displaying a highlighted outline. This helps users identify which part of the web page is capturing their key presses. You can usually disable this outline by adding outline: none; to the canvas's CSS styles.