Mobile SEO Checklist: Viewport, Touch Targets & Performance Interactive checklist for mobile-friendliness with best practices and fix instructions.

The tool works by iterating over a predefined array of checks, each representing a specific mobile-friendliness criterion, such as viewport configuration, touch target sizes, and image responsiveness. This array is defined in the `CHECKS` constant, which contains objects with properties like `id`, `cat`, `label`, `desc`, `impact`, and `fix`. The `CATS` constant is derived from the unique categories present in the `CHECKS` array, using the `Set` data structure to eliminate duplicates. The tool then uses React's `useState` hook to manage the state of each check, tracking which ones have been passed or failed.

When a user interacts with the tool, it updates the state accordingly, recalculating the mobile-friendliness score based on the number of passed checks. This score is displayed as a percentage, along with a visual representation using an SVG progress circle. The tool also uses CSS classes to apply different styles based on the impact level of each check, such as critical, high, or medium. The `ic` function maps impact levels to specific CSS classes, which are then applied to the corresponding elements.

In terms of technologies used, the tool relies on React for building the user interface and managing state, while also leveraging CSS for styling and layout. The code uses TypeScript for type checking and ensures that the component is rendered on the client-side using the `'use client'` directive. The `MobileFriendlyCheckerGuide` component returns a JSX element that contains the interactive checklist, which is generated dynamically based on the `CHECKS` array. Each check is represented by a button that toggles its state when clicked, and a detailed description of the issue and its fix are displayed when the user expands the corresponding section.