A fast page is mostly arithmetic.

Good interfaces feel like taste. Underneath, a few fixed limits decide most of what works.

Four numbers every interface answers to

Frame budget
16.7 ms
What a browser gets to draw one frame at 60 hertz.
Text contrast
4.5 : 1
The ratio body text needs against its background to pass AA.
Touch target
44 px
The size to reach for wherever a missed tap costs the most.
Flow of thought
1,000 ms
About how long a wait can last before a person stops feeling in control.