Some incomprehensible TeX commands for your document preamble that might make your university assignments a bit more fun

preamble.tex

%
% MATHS
%
\usepackage[table]{xcolor}    % loads also »colortbl«
\usepackage[many]{tcolorbox}
\usepackage{mathtools}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{physics}
\usepackage{mathspec}
\setallmainfonts(Digits,Latin,Greek){TeX Gyre Pagella Math}
\setmathrm{TeX Gyre Pagella}
\usepackage{fontspec}

%\setmainfont{Tex Gyre Pagella}
%\setSansfont{CMU Sans Sans}

\setmainfont[
    Path=media/,
    BoldFont=NotoSans-Bold.ttf,
    ItalicFont=NotoSans-Italic.ttf,
    BoldItalicFont=NotoSans-BoldItalic.ttf
]{NotoSans-Regular.ttf}
\setmonofont[
    Path=media/,
    BoldFont=NotoSans-Bold.ttf,
]{NotoSans-Regular.ttf}
\usepackage{polyglossia}
\newfontfamily\greekfonttt[Path=media/,BoldFont=Cousine-Bold.ttf,Script=Greek]{Cousine-Regular.ttf}
\newfontfamily\greekfontsf[Script=Greek]{DejaVuSans.ttf}
\setmainlanguage[numerals=arabic]{greek}



%\setmathfont{Neo Euler}
%\setmathrm{Alegreya}
%\setmathfont[range=it]{Alegreya-Italic}
%\setmathfont[range=bfit]{Alegreya-BoldItalic}
\setmathfont[range={}]{TeX Gyre Pagella Math} % empty range to get the correct metrics


%
% HYPERLINKS
%
\usepackage{hyperref}
\hypersetup{colorlinks,linkcolor={blue!40!black!90!green},citecolor={blue!50!black},urlcolor={cyan!60!blue!70!black}}

%
% VARIOUS OTHER PACKAGES
%
\usepackage[left=2cm,right=2cm,top=2cm,bottom=2cm]{geometry}
%\usepackage[disable]{todonotes}
%\usepackage[normalem]{ulem}
%\usepackage{color}

%\usepackage{graphicx}
%\usepackage{wrapfig}
%\usepackage{listings}
\usepackage{trace}
\renewcommand*{\figurename}{Εικόνα}
\usepackage{caption}
\usepackage{subcaption}
\usepackage[title,page,titletoc]{appendix}
%\usepackage{floatrow}
\usepackage{xfrac}
\usepackage[alsoload=binary]{siunitx}
\usepackage{setspace}
\usepackage{afterpage}
\usepackage{pagecolor}
\usepackage{wrapfig}
\usepackage{svg}
\usepackage[inline]{enumitem}

\newcommand\numberthis{\addtocounter{equation}{1}\tag{\theequation}}

%
% TIKZ
%
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\pgfplotsset{plot coordinates/math parser=false}
\usepackage{tikz}                       %inline graphics
\usetikzlibrary{plotmarks,chains,calc,shapes.geometric}
\usetikzlibrary{hobby,backgrounds,trees,snakes,shapes.callouts,positioning,pgfplots.groupplots}
\usetikzlibrary{shapes.geometric}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{patterns,shadows}
\usepackage[outline]{contour}

%
% Source: https://tex.stackexchange.com/questions/269080/sketching-an-acoustic-scenario-head-and-loudspeakers-in-tikz
%
\definecolor{skin}{RGB}{248,198,135}
\definecolor{mygreen}{RGB}{66,213,0}
\newcounter{speaker}
\tikzset{
  Speaker/.pic={
    \filldraw[fill=gray!40,pic actions] 
    (-15pt,0) -- 
      coordinate[midway] (-front) 
    (15pt,0) -- 
    ++([shift={(-6pt,8pt)}]0pt,0pt) coordinate (aux1) -- 
    ++(-18pt,0) coordinate (aux2) 
    -- cycle 
    (aux1) -- ++(0,6pt) -- coordinate[midway] (-back) ++(-18pt,0) -- (aux2);
  },
  Human/.pic={
    \filldraw[fill=mygreen] 
      (0,0.7cm) ellipse [x radius=10pt,y radius=5pt]
      (0,-0.7cm) ellipse [x radius=10pt,y radius=5pt];    
    \filldraw[fill=skin] 
      (0.7,4pt) -- (0.7,-4pt) -- (0.95,0pt) -- cycle;    
    \filldraw[fill=skin] 
      (0,0) ellipse [x radius=0.8cm, y radius=0.7cm];
    \filldraw[fill=brown!85!black] 
      (0.5,0.55) arc[start angle=50,end angle=310,x radius=0.8cm, y radius=0.7cm]
      to[out=60,in=230] cycle;
    \filldraw[fill=mygreen,rounded corners]
      (-0.2,0.75) -- (0.2,0.75) -- (0.2,-0.75) -- (-0.2,-0.75) -- cycle;  
  }
}
\newcommand{\coolgraphic}{\begin{tikzpicture}
\foreach \Radius/\Shade in {4.2/10,4.1/20,4/40,3.9/60,3.8/80}
\fill[mygreen!\Shade]
  (0,0) circle [radius=\Radius];
\fill[white]
  (0,0) circle (3cm);
\foreach \Angle [count=\xi] in {0,30,60,140,280}
  \pic[rotate=\Angle-90] (sp\xi) at (\Angle:3cm) {Speaker};
\draw[dashed]
  (210:4.2cm) -- (30:4.2cm)
  (120:4.2cm) -- (300:4.2cm);
\pic[rotate=30] {Human};
% draw some arrows from and to the speakers
\draw[-latex] (sp1-front) -- ++(-10pt,0pt);
\draw[-latex] (sp1-back) -- ++(10pt,0pt);
\draw[latex-] (sp3-front) -- ++(240:10pt);
\draw[latex-] (sp3-back) -- ++(60:10pt);
\end{tikzpicture}}

%
% MISC
%
\renewcommand*{\figureautorefname}{Εικόνα}
\renewcommand*{\sectionautorefname}{Ενότητα}
\renewcommand*{\subsectionautorefname}{Ενότητα}
\renewcommand*{\subsubsectionautorefname}{Ενότητα}
\renewcommand*{\tableautorefname}{Πίνακας}
\newcommand*{\algorithmautorefname}{Αλγόριθμος}
\renewcommand{\appendixpagename}{Παραρτήματα}
\newcommand{\Παράρτημαautorefname}{Παράρτημα}


%
% INSTRUCTIONS
%
\usepackage[format=plain,
            labelfont={bf,it},
            textfont=it]{caption}

\usepackage{chngcntr}
%\counterwithin{figure}{section}
%\counterwithin{table}{section}

\renewcommand*{\figurename}{Εικόνα}
\addto\captionsgreek{%
	\renewcommand{\figurename}{Εικόνα}%
}

%
% BACKGROUND
%
\usepackage[pages=some]{background}
\backgroundsetup{
scale=1,
color=white,
opacity=.5,
angle=0,
contents={%
  \includegraphics[height=\paperheight]{background}
  }%
}

\DeclareSIUnit\decibel{dB}
\DeclareSIUnit\bit{b}
\DeclareSIUnit\dbm{dBm}
\DeclareSIUnit\dbw{dBW}
\DeclareSIUnit\dbi{dBi}
\DeclareSIUnit\dbd{dBd}
\sisetup{range-phrase=-}

\usepackage{listings}
\lstset{frame=tb,
	language=Matlab,
	aboveskip=1mm,
	belowskip=1.5mm,
	xleftmargin=0mm,
	xrightmargin=0mm,
    framexleftmargin=0mm,
    framexrightmargin=0mm,
	rulesep=0mm,
	framesep=2mm,
	framexbottommargin=0mm,
	framextopmargin=0mm,
	%frame=none,
	xleftmargin=\parindent,
	numbersep=5pt,
	showstringspaces=false,
	columns=flexible,
	keepspaces=true,
	basicstyle={\footnotesize\ttfamily},
	numbers=none,
	numberstyle=\tiny\color{gray},
	keywordstyle=\color{blue},
	commentstyle=\color{cyan},
	stringstyle=\color{magenta!50!blue},
	%breaklines=true,
%	breakatwhitespace=true,
	tabsize=3,
	backgroundcolor=\color{blue!30!gray!20!white}
}

% My tcolorboxes
\tcbset{note/.style={
		enhanced,
		%rightrule=0pt,
		%toprule=0pt,
		outer arc=0pt,
		arc=0pt,
		colframe=black!90!white,
		colback=white,
		attach boxed title to top left,
		boxed title style={
			colback=black!90!white,
			outer arc=0pt,
			arc=0pt,
			top=3pt,
			bottom=3pt,
		}
	}
}


\usepackage[explicit]{titlesec}
\usepackage{ulem}
\normalem

%\setcounter{secnumdepth}{4}
%\titleformat{\paragraph}[runin]
%{\normalfont\normalsize\bfseries}{}{15pt}{\uline{\theparagraph\hspace*{1em}#1.}}
%\titleformat{name=\paragraph,numberless}[runin]
%{\normalfont\normalsize\bfseries}{}{15pt}{\uline{#1.}}