I just downloaded and tried out an app called &quot;Time to code - learn HTML, CSS and JavaScript.&quot; I have never used it to teach (and only downloaded it in response to this Ask HN). But, what I have seen is actually quite good! It might get a bit boring for teenagers, but as a learning tool, it seems pretty decent.<p>(Also note that I&#x27;m 38 so I&#x27;m not a very good judge of what teenagers would enjoy.)