user6593: How is this effect achieved?
https://imgur.com/c5fyRDp
(Original video: 

)

user25485: The instructor is just standing behind glass and writing on it.

6593: <p>How is this effect achieved?</p>

<p><a href="https://imgur.com/c5fyRDp" rel="nofollow noreferrer">https://imgur.com/c5fyRDp</a></p>

<p>(Original video: <div class="youtube-embed"><div>
                <iframe width="640px" height="395px" src="https://www.youtube.com/embed/nJZm-zp639s?start=0"></iframe>
            </div></div>)</p>
 25485: <p>The instructor is just standing behind glass and writing on it.</p>
