Instead of the work I was supposed to do I spent about a day and a half on the alpha version of a viewports visualisation app that, oh irony of ironies, only works on desktop browsers because of the necessary space.
It’s already been very useful to me, since figuring out how the viewports actually work is necessary for full understanding. I hope it does the same for you.
It also contains an example of absolute, fixed, and device-fixed position so that you understand the difference.
The app is by no means ready; there’s a ton of features I’d like to add. Still, for now I’ve run out of time, and as long as it’s impossible to actually make money with such apps I’m not sure how much time I’m willing to spend on it.