\documentclass[options]{class}

\documentclass[12pt,a4paper,twocolumn,draft]{article}

\documentclass[12pt,a4paper]{article}

% === PREAMBLE ===
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amssymb}
\usepackage{graphicx}
\usepackage{hyperref}

\title{My Document}
\author{Author Name}
\date{\today}

% === BODY ===
\begin{document}
\maketitle
\tableofcontents

\section{Introduction}
Content here.

\end{document}

\tiny  \scriptsize  \footnotesize  \small  \normalsize
\large  \Large  \LARGE  \huge  \Huge

\begin{center}    Centered text.    \end{center}
\begin{flushleft} Left-aligned.     \end{flushleft}
\begin{flushright} Right-aligned.   \end{flushright}

\vspace{1cm}          % vertical space
\hspace{2em}          % horizontal space
\vfill                % stretch vertical
\hfill                % stretch horizontal
\\[0.5cm]             % line break with extra space
\setlength{\parskip}{0.5em}   % paragraph spacing
\setlength{\parindent}{0pt}   % remove paragraph indent
\noindent             % suppress indent for one paragraph

\usepackage{setspace}
\onehalfspacing    % or \doublespacing, \singlespacing

\part{Part Title}           % only in report/book
\chapter{Chapter Title}     % only in report/book
\section{Section}
\subsection{Subsection}
\subsubsection{Subsubsection}
\paragraph{Paragraph}
\paragraphsub{Subparagraph}

\tableofcontents    % requires two compilations
\listoffigures
\listoftables

% Bulleted
\begin{itemize}
  \item First item
  \item Second item
\end{itemize}

% Numbered
\begin{enumerate}
  \item First
  \item Second
\end{enumerate}

% Labeled
\begin{description}
  \item[Term] Definition here.
\end{description}

\usepackage{enumitem}
\begin{enumerate}[label=(\alph*), start=1]

\section{Methods}\label{sec:methods}
See Section~\ref{sec:methods} on page~\pageref{sec:methods}.

This has a footnote.\footnote{Footnote text here.}

Inline: $E = mc^2$ or \(E = mc^2\)

Display:
\[ E = mc^2 \]

% Numbered equation:
\begin{equation}\label{eq:einstein}
  E = mc^2
\end{equation}

\usepackage{amsmath}    % align, cases, matrices, etc.
\usepackage{amssymb}    % extra symbols (ℝ, ℤ, etc.)
\usepackage{mathtools}  % extends amsmath (dcases, coloneqq, etc.)

% Fractions
\frac{a}{b}          \dfrac{a}{b}  (display-size)

% Roots
\sqrt{x}             \sqrt[3]{x}

% Sub/superscripts
x_{i}   x^{2}   x_{i}^{2}   a_{i,j}

% Sums, products, integrals
\sum_{i=1}^{n} x_i      \prod_{i=1}^{n} x_i
\int_{0}^{\infty} f(x)\,dx
\lim_{x \to \infty} f(x)

% Brackets (auto-sized)
\left( \frac{a}{b} \right)
\left[ ... \right]
\left\{ ... \right\}

\begin{pmatrix} a & b \\ c & d \end{pmatrix}   % (a b; c d)
\begin{bmatrix} a & b \\ c & d \end{bmatrix}   % [a b; c d]
\begin{vmatrix} a & b \\ c & d \end{vmatrix}   % |a b; c d| (determinant)
\begin{Bmatrix} a & b \\ c & d \end{Bmatrix}   % {a b; c d}

\begin{align}
  f(x) &= x^2 + 2x + 1 \label{eq:f} \\
  g(x) &= x^3 - 1       \label{eq:g}
\end{align}

% No numbering:
\begin{align*}
  a &= b + c \\
  d &= e + f
\end{align*}

f(x) = \begin{cases}
  x^2  & \text{if } x \geq 0 \\
  -x^2 & \text{if } x < 0
\end{cases}

\begin{table}[htbp]
  \centering
  \caption{Results summary}\label{tab:results}
  \begin{tabular}{lcrp{4cm}}
    \toprule
    Name & Count & Score & Description \\
    \midrule
    Alpha & 10 & 95.2 & First entry \\
    Beta  & 20 & 87.1 & Second entry \\
    \bottomrule
  \end{tabular}
\end{table}

\usepackage{booktabs}   % \toprule, \midrule, \bottomrule (professional rules)
\usepackage{multirow}   % \multirow{nrows}{width}{text}
\usepackage{longtable}  % tables spanning multiple pages
\usepackage{tabularx}   % auto-width X columns

\multicolumn{3}{c}{Spanning header} \\
\multirow{2}{*}{Tall cell}

\usepackage{graphicx}

\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.8\textwidth]{images/photo.png}
  \caption{A descriptive caption.}\label{fig:photo}
\end{figure}

\usepackage{subcaption}

\begin{figure}[htbp]
  \centering
  \begin{subfigure}[b]{0.48\textwidth}
    \includegraphics[width=\textwidth]{img1.png}
    \caption{First}\label{fig:sub1}
  \end{subfigure}
  \hfill
  \begin{subfigure}[b]{0.48\textwidth}
    \includegraphics[width=\textwidth]{img2.png}
    \caption{Second}\label{fig:sub2}
  \end{subfigure}
  \caption{Both images}\label{fig:both}
\end{figure}

@article{smith2023,
  author  = {Smith, John and Doe, Jane},
  title   = {An Important Paper},
  journal = {Journal of Examples},
  year    = {2023},
  volume  = {42},
  pages   = {1--15},
  doi     = {10.1234/example}
}

@book{knuth1984,
  author    = {Knuth, Donald E.},
  title     = {The {\TeX}book},
  publisher = {Addison-Wesley},
  year      = {1984}
}

\usepackage{natbib}  % or use biblatex
\bibliographystyle{plainnat}

As shown by \citet{smith2023}...  % Smith and Doe (2023)
This is known \citep{smith2023}.  % (Smith and Doe, 2023)

\bibliography{references}

\usepackage[backend=biber, style=authoryear]{biblatex}
\addbibresource{references.bib}

\textcite{smith2023}   % Smith and Doe (2023)
\parencite{smith2023}  % (Smith and Doe, 2023)

\printbibliography

\begin{verbatim}
def hello():
    print("Hello, world!")
\end{verbatim}

Inline: \verb|some_code()|

\usepackage{listings}
\usepackage{xcolor}

\lstdefinestyle{mystyle}{
  basicstyle=\ttfamily\small,
  keywordstyle=\color{blue},
  commentstyle=\color{gray},
  stringstyle=\color{red},
  numbers=left,
  numberstyle=\tiny,
  frame=single,
  breaklines=true
}

\begin{lstlisting}[language=Python, style=mystyle, caption={Example}]
def factorial(n):
    """Compute factorial."""
    if n <= 1:
        return 1
    return n * factorial(n - 1)
\end{lstlisting}

\usepackage{minted}

\begin{minted}[linenos, frame=lines, fontsize=\small]{python}
def factorial(n):
    if n <= 1:
        return 1
    return n * factorial(n - 1)
\end{minted}

\documentclass{beamer}
\usetheme{Madrid}          % or: Berlin, Warsaw, Metropolis, etc.
\usecolortheme{default}    % or: beaver, crane, dolphin, etc.

\title{My Presentation}
\author{Author}
\date{\today}

\begin{document}

\begin{frame}
  \titlepage
\end{frame}

\begin{frame}{Outline}
  \tableofcontents
\end{frame}

\section{Introduction}
\begin{frame}{Introduction}
  \begin{itemize}
    \item<1-> First point (appears on slide 1+)
    \item<2-> Second point (appears on slide 2+)
    \item<3-> Third point
  \end{itemize}
\end{frame}

\begin{frame}{With Columns}
  \begin{columns}
    \begin{column}{0.5\textwidth}
      Left content
    \end{column}
    \begin{column}{0.5\textwidth}
      Right content
    \end{column}
  \end{columns}
\end{frame}

\end{document}

\usepackage[margin=2.5cm]{geometry}
% or:
\usepackage[top=3cm, bottom=3cm, left=2cm, right=2cm]{geometry}

\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhf{}                          % clear all
\fancyhead[L]{Left Header}
\fancyhead[R]{\rightmark}          % current section
\fancyfoot[C]{\thepage}            % page number center
\renewcommand{\headrulewidth}{0.4pt}

\pagenumbering{roman}   % i, ii, iii (for front matter)
\pagenumbering{arabic}  % 1, 2, 3 (for main content)
\thispagestyle{empty}   % no number on this page

\usepackage{multicol}
\begin{multicols}{2}
  Content in two columns...
\end{multicols}

# Basic document
pdflatex document.tex

# With bibliography (BibTeX)
pdflatex document.tex
bibtex document
pdflatex document.tex
pdflatex document.tex

# With bibliography (Biber/BibLaTeX)
pdflatex document.tex
biber document
pdflatex document.tex
pdflatex document.tex

# Automated (recommended)
latexmk -pdf document.tex           # pdflatex
latexmk -xelatex document.tex       # xelatex
latexmk -lualatex document.tex      # lualatex
latexmk -pdf -pvc document.tex      # continuous preview