Build JavaScript Course Platform

I already sketched a responsive HTML / CSS front end for an online learning site and need an expert to turn it into a polished platform that centres on Programming courses—specifically intermediate-level JavaScript.

The structure is in place: pages load, breakpoints behave, and the colour palette meets WCAG contrast ratios. Your job is to refine the interface, wire up the course catalogue, and make the whole journey—from category overview to lesson page—feel effortless on desktop, tablet, and mobile.

What I expect from you
• Clean, semantic HTML5 and modern, component-based CSS (Flexbox / Grid) that keep accessibility top of mind.
• JavaScript that powers course filtering, search, and smooth navigation without bloating performance.
• Dedicated course pages that support text, code snippets, and media for an intermediate audience.
• Clear organisation so future courses or languages could slot in easily.
• Cross-browser testing and a quick hand-off guide explaining file structure and how to add new JavaScript lessons.

Acceptance criteria
1. Users can browse the Programming category and see only JavaScript courses tagged “Intermediate.”
2. Each course page loads in under 2 s on a 3G connection and passes Lighthouse scores of 90 + for Performance, Accessibility, and Best Practices.
3. Layout adapts flawlessly from 320 px up to 1440 px without horizontal scroll.
4. All interactive elements are keyboard-navigable and announce proper ARIA roles.

If you thrive on crafting accessible, responsive interfaces and know your way around vanilla JavaScript (or a lightweight framework if it helps), I’d love to see how you’d elevate this project. Share one or two links that show similar course or content-heavy sites you’ve built, and include a quick outline of the tools or build process you prefer.