The built-in inspector for editing styles live, with editors for grid, flexbox, colours, shadows, easing and container queries.

The developer tools built into Chrome. The Styles tab shows every rule that matches an element, including overridden ones, and Computed shows only what applies. You can edit declarations, toggle classes and force states like :hover.
It has visual editors for colours (including HD colours), shadows, easing curves, angles and grid alignment, and it shows cascade layers, @property, @scope, @supports and @position-try rules. It highlights invalid, overridden and inactive CSS.
Other tools include the Coverage tab for unused CSS, dark mode and print emulation, and copying CSS as declarations, rules or JavaScript.
gridcontainer querieslinear()