The DOM Element or its ID that will contain Engine. If there is no such element found, an uncatchable error will be thrown. If nothing was provided, a new DOM Element will be created by the Engine.
ID of the DOM element that will contain Engine. If there is no such element found on the document, an uncatchable error will be thrown.
Interface specifies that Engine should not think about its own size and simply fit itself into an existing element on the document, which should be created by user.