Also: <https://www.toonhoundstudios.com/comic/20001202/?sid=372>

Off topic, XKCD should put the original publication date on the page. This one references specific years, and I could tell it's from 2009 after thinking about it, but doesn't hit the same way.

I've never played enough Portal to get to the point referred to by the comic, but I get the idea.

And yes, I probably played Portal 1 a few years after Portal 2 was out.

I tend to read this shortly after the strip, because I am that stupid. Also because there is no easy mouseover on android. https://www.explainxkcd.com/wiki/index.php/606:_Cutting_Edge

m.xkcd.com lets you click for the alt-text.