Responsive Vanilla JS Website Build

I’m starting this project from a blank folder and need a fully responsive website crafted with pure HTML5, CSS3 and Vanilla JavaScript. My priority is a clean, modern UI that feels just as smooth on a phone as it does on a desktop.

Core features I’m looking for:
• A modern, accessible navigation menu (I’m flexible on whether it’s horizontal, vertical or hamburger, as long as it looks sharp on all screen sizes).
• An interactive Services section that highlights what we offer with subtle, elegant motion.
• A dynamic contact form that validates fields in-browser before submission and provides clear inline feedback.

The site should include tasteful CSS transitions—think gentle fades or slides rather than flashy effects—and all components must be coded from scratch, no frameworks. Please keep the markup semantic, the styles organised, and the JavaScript modular. Comments should explain any non-obvious logic so future edits are straightforward.

Final deliverable is the full project folder ready to deploy, with every line tested across modern browsers and mobile devices.