v4.0 is less a redesign than a hard edit. Three colour families only: blue, green, violet. Amber, gold and yellow are banned outright. Sharp corners everywhere — border-radius is zero, no exceptions. Courier Prime is the typeface, always.
A tight system is faster to build with and harder to get wrong. When there are only three colours and one font, every new screen composes itself.
v4 is the version every app in the ecosystem now inherits, top to bottom.