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Full use of CSS-in-JS techniques. There are still many conflicting opinions about the merits (or lack thereof) of putting styling logic in Javascript rather than a dedicated CSS stylesheet, and there are already 123078354232 other blog posts that discuss this. CSS-in-JS finds its place in React Elemental primarily because it eliminates the need for the client project to import external CSS (which in itself might warrant adding css-loader and style-loader to the project's Webpack configuration, if it doesn't already use CSS). It also nicely scopes styling properties to only the components themselves, eliminating the possibility of Elemental style declarations "leaking" into other elements in the project due to unfortunate name clashing.
Maximum client flexibility and customizability. A UI library can have opinions, but those opinions should not hinder the ability of the client to override its presention or behavior. The library should provide intuitive interfaces to allow clients to customize component styling and a component's internal behavior.
Minimal configuration and maximum development velocity. It should not require an inordinate amount of time to incorporate the UI library into an existing application. Using the library should be a matter of npm install, invoking a bootstrapping/initialization function, and then importing a component and expecting it to render exactly as shown in example documentation.
Clear lines separating responsibilities, enforced by a clean API. A UI library should strive to be primarily presentational in nature, and should not try to do "too much." A UI component should draw clear lines of responsibility between itself and the parent component (client), delegating certain logic to the parent rather than trying to manage it itself.

Almost all styling is done with inline styles on the UI component nodes themselves. (There are some things that can't be done purely with inline styles, like @font-face declarations or animation keyframes, and these are written in regular CSS. However, these declarations are injected automatically and transparently, and does not require configuration changes or CSS imports by the client application.)
All components accept a style prop that allows the client to override any style properties. Whenever possible, visual parameters (like the thickness of a Spinner, color of a LoadingBar, etc.) can be adjusted with an explicit prop on the component. All components transparently proxy all non-component props to the underlying container, allowing the client to specify (for example) event handlers like onMouseDown or onClick without needing the needlessly wrap the component with an additional parent node.
All stateful initialization procedures are contained with a single function, bootstrap, exported by react-elemental. It only needs to be called once alongside the rest of the client application's initialization logic, and all bootstrapping parameters are optional.
Each stateful component has clear APIs describing how responsibilities between the parent component and Elemental UI component are divided. Generally, the UI components are presentational in nature, delegating state management logic to the parent component (see Controlled Components).

$ npm install react-elemental

import { bootstrap } from 'react-elemental';

bootstrap();

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