Dictionary

CSS Animation uses `@keyframes` rules and the `animation` property to create complex, multi-step animations entirely in CSS without JavaScript. Combined with CSS transitions for simple state changes, these tools handle most UI animation needs performantly since browsers can optimize them on the GPU compositor thread. Properties like `transform` and `opacity` are particularly efficient to animate because they don't trigger layout recalculations or repaints.

CSS Custom Properties (also called CSS Variables) let you define reusable values with `--my-variable` syntax and reference them anywhere using `var(--my-variable)`. Unlike preprocessor variables in Sass or Less, they are live in the browser, cascade through the DOM, and can be updated dynamically with JavaScript. They're essential for theming systems, dark mode implementations, and maintaining consistent design tokens across large stylesheets.

CSS Grid is a two-dimensional layout system that lets you define rows and columns simultaneously, making it ideal for complex page layouts. Unlike Flexbox which works in one axis at a time, Grid allows you to place items precisely in both horizontal and vertical directions using named areas or line numbers. Features like `grid-template-areas`, `auto-fill`, and `minmax()` make it possible to create responsive layouts with minimal code.

CSS Modules are CSS files where all class names are locally scoped by default, meaning they're automatically transformed into unique identifiers at build time to prevent naming collisions. You import them into your JavaScript as an object and reference classes like `styles.button` instead of plain strings. This approach is natively supported by bundlers like Webpack, Vite, and Next.js, offering style isolation without the runtime overhead of CSS-in-JS.

CSS-in-JS is an approach where styles are written directly in JavaScript files, often co-located with the components they style. Libraries like Styled Components, Emotion, and Stitches generate unique class names at build time or runtime, eliminating style conflicts. While it enables dynamic styling based on props and full encapsulation, the trend has shifted toward zero-runtime solutions and utility-first CSS due to performance concerns.

Chain of Thought (CoT) is a prompting technique that encourages an LLM to break down complex reasoning into intermediate steps before arriving at a final answer. By explicitly reasoning through each step, models achieve significantly better accuracy on math, logic, and multi-step problems. Extended thinking and "thinking" tokens in models like Claude represent a built-in form of chain-of-thought reasoning.

Code splitting is an optimization technique that breaks a JavaScript bundle into smaller chunks that are loaded on demand, rather than forcing users to download the entire application upfront. In React, this is achieved through `React.lazy()` and dynamic `import()` statements, which create separate bundles loaded only when the corresponding component or route is accessed. This dramatically improves initial load times, especially for large single-page applications with many routes.

Cognitive load refers to the amount of mental effort required to use an interface. In UX design, reducing cognitive load means simplifying choices, minimizing distractions, and presenting information progressively so users aren't overwhelmed. Techniques like consistent layouts, clear visual hierarchy, familiar patterns, and sensible defaults all help keep cognitive load manageable and allow users to focus on their actual tasks.

Color contrast is the measurable difference in luminance between foreground text (or UI elements) and their background. WCAG guidelines require a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text to ensure readability for users with visual impairments. Tools like Chrome DevTools, Stark, and WebAIM's contrast checker help developers verify compliance during development.

A component library is a curated set of pre-built, reusable UI elements — buttons, inputs, modals, cards — packaged for consistent use across projects. Libraries like Material UI, Chakra UI, or Radix provide accessible, themeable building blocks so developers don't have to reinvent common patterns. A well-maintained component library drastically reduces development time and ensures visual consistency throughout an application.

Computer vision is a field of AI that trains machines to interpret and understand visual information from images and videos. Applications include object detection, facial recognition, autonomous driving, and medical image analysis. Modern computer vision leverages deep learning models like CNNs and vision transformers (ViT), and increasingly integrates with language models in multimodal AI systems.

Container Queries allow CSS styles to respond to the size of a parent container rather than the browser viewport, solving a long-standing limitation of media queries. By marking an element as a containment context with `container-type`, its children can use `@container` rules to adapt their layout based on the container's dimensions. This makes truly reusable components possible — a card component can rearrange itself whether it's in a sidebar or a full-width section.