Testing Post 2

This is the starter

Charts

Posts support interactive charts. Write a fenced code block tagged chart with a JSON body and the renderer draws the graph. Hover a chart to inspect values; click a line-chart legend item to toggle that series.

Line chart

Provide shared labels for the x-axis and one or more series, each with its own values. Optional smooth and area flags.

• Reading
• Listening
• Speaking

A series can instead be described as { "x": ..., "y": ... } points:

• Minutes

Pie chart

Use slices, each with a label and value. Add "donut": true for a donut variant. Hover a slice (or its legend entry) to highlight it.

• Reading66 (66.0%)
• Listening15 (15.0%)
• Speaking6.5 (6.5%)
• Kanji12.5 (12.5%)

Map chart

Draw routes from Point A to Point B on a draggable 3D globe. List the points (with lat/lng) and the routes between them; a route's from/to can reference a point by name or carry inline coordinates. Set "autoRotate": false to keep the globe still, and use the on-map button to toggle rotation. The route line itself stays fixed.

Rotate

• Diving trip
• Move to Japan

Math (LaTeX)

Posts render LaTeX with KaTeX. There are three ways to write it: $…$ for inline math, $$…$$ for a centred display block, and a fenced ```math block when the source deserves its own lines. Everything is typeset at build time, so no client-side script has to run for the formulas to show up.

Inline math

Wrap the expression in single dollar signs: Euler's identity, $e^{i\pi} + 1 = 0$, flows with the surrounding sentence, and so do symbols such as $\alpha$, $\Sigma$, $\sqrt{2}$, fractions like $\tfrac{3}{4}$ and comparisons such as $0 < \varepsilon \ll 1$.

Display math

Double dollar signs on their own lines centre the formula and give it room to breathe:

$$\int_{-\infty}^{\infty} e^{-x^{2}}\,dx = \sqrt{\pi}$$ $$\hat{f}(\xi) = \int_{-\infty}^{\infty} f(x)\, e^{-2\pi i x \xi}\,dx$$

Fenced math blocks

A fenced block tagged math is equivalent to $$…$$ and keeps long derivations readable in the source file:

$$\begin{aligned} (a + b)^2 &= a^2 + 2ab + b^2 \\ (a - b)^2 &= a^2 - 2ab + b^2 \\ (a + b)(a - b) &= a^2 - b^2 \end{aligned}$$

Environments such as aligned, cases, matrix and array all work:

$$f(n) = \begin{cases} n / 2 & \text{if } n \equiv 0 \pmod{2} \\ 3n + 1 & \text{if } n \equiv 1 \pmod{2} \end{cases}$$ $$A = \begin{bmatrix} 1 & 0 & 0 \\ 0 & \cos\theta & -\sin\theta \\ 0 & \sin\theta & \cos\theta \end{bmatrix}$$

Math inside other blocks

Formulas are allowed anywhere inline text is, including list items:

1. Arithmetic series: $\sum_{i=1}^{n} i = \frac{n(n+1)}{2}$
2. Geometric series: $\sum_{i=0}^{\infty} r^{i} = \frac{1}{1-r}$ for $|r| < 1$
3. Binomial coefficient: $\binom{n}{k} = \frac{n!}{k!\,(n-k)!}$

...and table cells:

Headings can hold math, like $a^2 + b^2 = c^2$

The table of contents on the right lists this section by the formula as it is drawn, and the heading's anchor link is still derived from the plain source.

Escaping dollar signs

A backslash keeps a dollar sign literal, so $5 and $10 stay plain text rather than opening a formula. Inline code is never parsed as math either, so $not math$ renders verbatim. A formula KaTeX cannot parse is shown in red where it sits instead of breaking the rest of the page.

Some photos