View Transitions API

Deep linking is the ability to direct users to a specific screen or content within a mobile or web application via a URL, rather than just opening the app's home screen. In React Native and Flutter, this involves configuring URL schemes (e.g., `myapp://profile/123`) or universal/app links that work across platforms. Deep linking is essential for push notification routing, marketing campaigns, sharing content between users, and creating seamless web-to-app transitions.

Styled Components is a popular CSS-in-JS library for React and React Native that uses tagged template literals to style components. It automatically generates unique class names, supports dynamic styling based on props, handles vendor prefixing, and provides full theming capabilities. The library colocates styles with components, making it easy to understand what each component looks like and to delete styles safely when removing components.

Accessibility (often abbreviated a11y) is the practice of designing and building websites and apps so they can be used by everyone, including people with visual, motor, auditory, or cognitive disabilities. This involves proper semantic markup, keyboard navigation support, sufficient color contrast, and screen reader compatibility. Beyond being an ethical responsibility, accessibility is increasingly a legal requirement in many jurisdictions.

Hot reload is a development feature that injects updated code into a running application without restarting it or losing the current state. In Flutter, hot reload works by injecting updated Dart source code into the running Dart VM, typically completing in under a second. React Native offers a similar feature called Fast Refresh that preserves component state during edits. Both dramatically accelerate the development feedback loop compared to traditional compile-and-restart cycles.

Design tokens are the smallest units of a design system — named values representing colors, spacing, typography, border radii, and other visual properties. They act as a single source of truth that can be translated into platform-specific formats (CSS variables, Swift constants, XML resources). By changing token values in one place, you can update the look and feel of an entire application across multiple platforms simultaneously.

Memoization in React is a performance optimization that caches the result of expensive computations or component renders to avoid redundant work on re-renders. React provides `React.memo()` to skip re-rendering a component when its props haven't changed, `useMemo()` to cache computed values, and `useCallback()` to cache function references. While powerful, premature memoization adds complexity — it's best applied after profiling confirms an actual performance bottleneck.