I'm using titlesec package to have a good style of the chapters and sections title. But now,
I would like to add a colored box around the chapter number and section number, I want to get the same style as the photo attached but I don't know how to do this. I prepared an example of what I'm using.
I'm using texshop.
\documentclass[a4paper,11pt,twoside,english]{book}
\usepackage[a4paper,top=2.5cm,bottom=2.5cm,left=3cm,right=2.5cm]{geometry}
\linespread{1.3}
\usepackage{titlesec}
\usepackage[Glenn]{fncychap}
\begin{document}
\chapter{The standard Model and beyond}
\section{The Standard Model of Particle physics}
\end{document}

\section, but not for\chapter): https://tex.stackexchange.com/questions/429441/beautiful-section-styles/429453#429453 – Skillmon Nov 29 '20 at 10:18fncychap? – Skillmon Nov 29 '20 at 10:23lua-ulwhich should be more robust thansoulandulem. – Skillmon Nov 29 '20 at 10:24