<div style="visibility:hidden;height:0;overflow:hidden;margin:0;padding:0">

```math
\newcommand{\LetThereBe}[2]{\newcommand{#1}{#2}} \newcommand{\letThereBe}[3]{\newcommand{#1}[#2]{#3}}
\letThereBe{\addTag}{2}{\cssId{#1-#2}{\tag{#2}}} \letThereBe{\refTag}{2}{\href{###1-#2}{(\text{#2})}}
\letThereBe{\eqT}{1}{\addTag{eq}{#1}}\letThereBe{\secT}{1}{\addTag{sec}{#1}}
\letThereBe{\eqRef}{1}{\refTag{eq}{#1}} \letThereBe{\secRef}{1}{\refTag{sec}{#1}}
\LetThereBe{\R}{\mathbb{R}} \LetThereBe{\N}{\mathbb{N}}
\letThereBe{\set}{1}{\left\{ #1 \right\}}
\letThereBe{\rcases}{1}{\left.\begin{align}#1\end{align}\right\}}
\letThereBe{\rcasesAt}{2}{\left.\begin{alignat}{#1}#2\end{alignat}\right\}}
\letThereBe{\lcases}{1}{\begin{cases}#1\end{cases}}
\letThereBe{\lcasesAt}{2}{\left\{\begin{alignat}{#1}#2\end{alignat}\right.}
\LetThereBe{\foo}{\mathrm{foo}}
```

</div>

# Math test simple

This does not render, $\foo$!

And

$$\set{x^2 \mid x \in \R \cap \N}. \eqT{square}$$

After some text we reference it as $\eqRef{square}$

```math
\begin{align} x &= 1 \\ y &= 2x + 3 \end{align}
```

now

```math
\rcases{x &= 1 \\ y &= 2x + 3} and \lcases{x &= 1 \\ y &= 2x + 3}
```
are we here???