Macaron is a typesafe CSS-in-JS library with zero runtime, colocation, maximum safety and productivity.
The motivation behind it is that runtime CSS-in-JS libraries, that is most of the CSS-in-JS libs, add alot of bloat to web apps and have a considerable performance drop with a bundle size increase. Alot of them also don't support more performant ways of building web apps like streaming markup. Most of the current compile-time CSS-in-JS libraries try to fix this, but have some or the other drawback like not offering colocation, or not being type-safe.
Today, Macaron does all this with a compiler that extracts all the style declarations at compile-time and converts them to static css files while also letting you author the type-safe styles in the same file as your application code. It supports both - a vanilla styling API and a styled-component API with support for multiple frameworks like SolidJS and React and build tools like Vite and Esbuild. Macaron is currently missing a webpack plugin, but that will also be published soon, making it compatible with almost all bundlers.
There's a ton of room for improvement in this space, and I feel like macaron is a step in that direction.