Just this once, I *had* to make a mega-menu. So, how could I make it less awful?

On a project where the Drupal 6 (& vBulletin & custom perl & even MovableType!) website had to stay there until it is all migrated, we had to find a way of making a responsive website in Drupal 8 that worked well on mobile yet looked essentially the same on desktop browsers. Even down to the incredibly verbose mega-menu...

I will be looking at the journey we took, finding out how we could store the content for the mega-menu, and how we could display it in a way that didn't totally destroy performance on mobile. I'll look at how I learned that "well, everything is an entity, just add a field!" doesn't really count everywhere in Drupal 8. I'll look at how some of the new parts of Drupal 8 allowed us to take a sideways look at how we achieved our goal and finally I'll have a look at how the solution we chose had a beneficial effect upon download performance and (possibly, I don't know, it's all snae oil to me) SEO...

I would best describe myself as a Site Builder happy to roll up her sleeves an learn a bit of code. I'd suggest that the pitch of the talk will be at a similar level. Having said that, I'm going to talk about principles, discussing ideas with the Dupal community and overall concepts. This is not a developer-only talk.