Quarto is becoming the default tool for technical reporting in the R ecosystem. It’s flexible, modern, and integrates cleanly with RStudio. But the default HTML themes often look generic — especially if you need professional‑grade reports for clients, research, or business presentations. In this guide, you’ll learn how to build a fully custom Quarto theme using pure CSS, without relying on any built‑in theme. This gives you complete control over typography, spacing, colors, and layout. Start With a Minimal Quarto Document Create a new .qmd file and disable the default theme: title : "Clean Quarto Theme" format : html : theme : null css : styles .css --- 2 . Create Your Custom CSS File Create a file named styles .css in the same directory .…