I have a question: After clicking on a blog in the listing page ("Collective Speed is..."), the page navigated to that particular blog. What CSS transitions are used to convert that title to a header? I saw some animation which pushed that title to become a header. How does that work? I'm curious

That'd be the View Transition API. Specifically, it is a cross-document view transition. https://developer.chrome.com/docs/web-platform/view-transiti...

Really awesome new(ish) feature of the web platform. It doesn't yet have full support in Firefox unfortunately, but is supported in Chrome and Safari.