R Markdown is one of the best tools for creating technical reports — but the default theme often looks outdated. A clean, modern theme makes your reports easier to read and more professional. In this guide, I’ll show you how to build a simple, reusable R Markdown theme you can apply to any project. --- title : " Clean R Markdown Theme" author : " Your Name" output : html_document : theme : null css : " style.css" --- We disable the default theme (theme : null ) so we can fully control the styling. Create a Custom CSS File body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; background: #f7f7f7; line-height: 1.6; color: #333; } h1, h2, h3 { font-weight: 600; color: #222; } code { background: #eee; padding: 2px 4px; border-radius: 4px; } pre { background: #272822; color: #f8f8f2; padding: 12px; border-radius: 6px; } This gives your report a clean, modern look.…