This is the <div> element stack which will host the canvas created by Button 1.
Button 2 removes the Button 1 canvas, wherever it is placed on the page.
Clicking Button 3 will delete the stack and, if present, the canvas. After clicking Button 3, creating a canvas with Button 1 will force that canvas to be added to the end of the web page.
Known issue: conversion to stack causes the stack element text to shrink on Android browser - possibly a FOUC problem?
Touch test: not required