YouTube-Style Video Site Prototype -- 2

I’ve drafted the core layout for a small “home page” that mimics YouTube, but I now want it polished into a clean, fully responsive front-end prototype.

Here’s what’s already in place:
• HTML, CSS, and JavaScript scaffolding built in Visual Studio Code
• A thumbnail gallery on the homepage, each card showing title, channel, and view count
• Sidebar navigation with Home, Shorts, Subscriptions, and Library
• Top search bar

What I still need you to complete or refine:
1. When a visitor clicks any video card, a sample pop-up player must appear on the same page (no redirects).
2. Populate the gallery with sample thumbnails and short demo clips rather than live YouTube embeds.
3. Tighten styling so the entire interface scales smoothly from mobile to desktop.
4. Optimise and organise the code for readability and easy future expansion.

I’m happy with vanilla HTML/CSS/JS, but feel free to use lightweight libraries if they help keep the bundle lean. The final deliverable should be a self-contained project folder I can open in VS Code and run locally by simply launching index.html.