Hello, Markdown!

This is a sample code block:

function greet() {
    console.log("Hello, world!");
}

And here is an inline formula: $E = mc^2$

And some block formula:

e^{\pi i} + 1 = 0

\left( \begin{array}{ccc} a & b & d \\ 0 & a & c \\ 0 & 0 & a \\ \end{array} \right)^n = \left( \begin{array}{ccc} a^n & n a^{n-1} b & n a^{n-2} \left[a d+\frac{1}{2} (n-1) b c\right] \\ 0 & a^n & n c a^{n-1} \\ 0 & 0 & a^n \\ \end{array} \right) , \quad n \in \mathbb{Z}^+

\int_0^\infty x^n e^{-x} \mathrm{d} x = n!

footnote

Here is a simple footnote¹.

A footnote can also have multiple lines².

A strange picture:

what

what?

Note

Highlights information that users should take into account, even when skimming.

Tip

Optional information to help a user be more successful.

Important

Crucial information necessary for users to succeed.

Warning

Critical content demanding immediate user attention due to potential risks.

Caution

Negative potential consequences of an action.

Caution

数域 $X$ 上的两个不相交的闭集 $A$ , $B$ 有可能可以并成 $X$ 。例如考虑 $\mathbb Q$ 上的集合

A = \{x\in \mathbb Q \mid x^2 <2 \}, \quad B = \{x\in \mathbb Q \mid x^2 > 2\}.

这两个集合在 $\mathbb Q$ 上都是既开又闭的，但 $A\cup B=\mathbb Q$ . 但是由于 $\mathbb R$ 是连通的，所以这种集合不存在。

My reference. ↩
To add line breaks within a footnote, prefix new lines with many spaces. This is a second line. ↩