There's a lot of lingo around the wider web so this is one of a series of short definition posts.
The web started out on desktop computers with pages that looked a lot like printed pages with new things called hyperlinks. Along came mobile phones and tablets and we made something called the "responsive web" that dynamically supports you no matter what device you're using to access the web.
Different screen sizes and touch input? No problem!
Page controls on the wider web usually appear in flat displays.
Page controls are one of the three types of controls on the wider web:
Using Three.js to build a reusable border geometry for spatial UIs!
🌸 Updated potassium style system (KSS), now with margins!
🌸 The path to the vNext
🌸 A couple of new spatial controls
🌸 A brief intro to the existing samples
🌸 Building UI components that work in flat, portal, and immersive display modes