HTML Viewer with Bidirectional Highlighting (Click Code ↔ Highlight Element)

I built this HTML Viewer because I was frustrated with existing tools that only let you view code or preview the page, but never link the two together. The core feature is bidirectional highlighting: Click any line of HTML/CSS in the editor → the corresponding element on the preview page is instantly highlighted and scrolled into view. Click any rendered element on the page → the editor jumps to and highlights the exact source line that generated it. This makes it way easier to debug, learn HTML/CSS, or teach frontend basics. It's built entirely with vanilla JavaScript, runs 100% client-side (no backend, no data collection), and is completely free to use. Would love to hear feedback on edge cases, feature ideas, or any bugs you find!