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+<!DOCTYPE html>
+<html lang="" xml:lang="">
+  <head>
+    <title>Presentation Ninja</title>
+    <meta charset="utf-8" />
+    <meta name="author" content="Mike - Test" />
+    <script src="libs/header-attrs/header-attrs.js"></script>
+    <link href="libs/remark-css/default.css" rel="stylesheet" />
+    <link href="libs/remark-css/default-fonts.css" rel="stylesheet" />
+    <link href="libs/htmltools-fill/fill.css" rel="stylesheet" />
+    <script src="libs/htmlwidgets/htmlwidgets.js"></script>
+    <script src="libs/jquery/jquery-3.6.0.min.js"></script>
+    <link href="libs/leaflet/leaflet.css" rel="stylesheet" />
+    <script src="libs/leaflet/leaflet.js"></script>
+    <link href="libs/leafletfix/leafletfix.css" rel="stylesheet" />
+    <script src="libs/proj4/proj4.min.js"></script>
+    <script src="libs/Proj4Leaflet/proj4leaflet.js"></script>
+    <link href="libs/rstudio_leaflet/rstudio_leaflet.css" rel="stylesheet" />
+    <script src="libs/leaflet-binding/leaflet.js"></script>
+    <link href="libs/datatables-css/datatables-crosstalk.css" rel="stylesheet" />
+    <script src="libs/datatables-binding/datatables.js"></script>
+    <link href="libs/dt-core/css/jquery.dataTables.min.css" rel="stylesheet" />
+    <link href="libs/dt-core/css/jquery.dataTables.extra.css" rel="stylesheet" />
+    <script src="libs/dt-core/js/jquery.dataTables.min.js"></script>
+    <link href="libs/crosstalk/css/crosstalk.min.css" rel="stylesheet" />
+    <script src="libs/crosstalk/js/crosstalk.min.js"></script>
+  </head>
+  <body>
+    <textarea id="source">
+class: center, middle, inverse, title-slide
+
+.title[
+# Presentation Ninja
+]
+.subtitle[
+## ⚔<br/>with xaringan
+]
+.author[
+### Mike - Test
+]
+.institute[
+### RStudio, PBC
+]
+.date[
+### 2016/12/12 (updated: 2026-01-23)
+]
+
+---
+
+
+background-image: url(https://upload.wikimedia.org/wikipedia/commons/b/be/Sharingan_triple.svg)
+
+
+
+???
+
+Image credit: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Sharingan_triple.svg)
+
+---
+class: center, middle
+
+# test
+
+### /ʃaː.'riŋ.ɡan/
+
+---
+class: inverse, center, middle
+
+# Get Started
+
+---
+
+# Hello World
+
+Install the **xaringan** package from [Github](https://github.com/yihui/xaringan):
+
+
+``` r
+remotes::install_github("yihui/xaringan")
+```
+
+--
+
+You are recommended to use the [RStudio IDE](https://www.rstudio.com/products/rstudio/), but you do not have to.
+
+- Create a new R Markdown document from the menu `File -&gt; New File -&gt; R Markdown -&gt; From Template -&gt; Ninja Presentation`;&lt;sup&gt;1&lt;/sup&gt;
+
+--
+
+- Click the `Knit` button to compile it;
+
+--
+
+- or use the [RStudio Addin](https://rstudio.github.io/rstudioaddins/)&lt;sup&gt;2&lt;/sup&gt; "Infinite Moon Reader" to live preview the slides (every time you update and save the Rmd document, the slides will be automatically reloaded in RStudio Viewer.
+
+.footnote[
+[1] 中文用户请看[这份教程](https://slides.yihui.org/xaringan/zh-CN.html)
+
+[2] See [#2](https://github.com/yihui/xaringan/issues/2) if you do not see the template or addin in RStudio.
+]
+
+---
+background-image: url(https://github.com/yihui/xaringan/releases/download/v0.0.2/karl-moustache.jpg)
+background-position: 50% 50%
+class: center, bottom, inverse
+
+# You only live once!
+
+---
+
+# Hello Ninja
+
+As a presentation ninja, you certainly should not be satisfied by the "Hello World" example. You need to understand more about two things:
+
+1. The [remark.js](https://remarkjs.com) library;
+
+1. The **xaringan** package;
+
+Basically **xaringan** injected the chakra of R Markdown (minus Pandoc) into **remark.js**. The slides are rendered by remark.js in the web browser, and the Markdown source needed by remark.js is generated from R Markdown (**knitr**).
+
+---
+
+# remark.js
+
+You can see an introduction of remark.js from [its homepage](https://remarkjs.com). You should read the [remark.js Wiki](https://github.com/gnab/remark/wiki) at least once to know how to
+
+- create a new slide (Markdown syntax&lt;sup&gt;*&lt;/sup&gt; and slide properties);
+
+- format a slide (e.g. text alignment);
+
+- configure the slideshow;
+
+- and use the presentation (keyboard shortcuts).
+
+It is important to be familiar with remark.js before you can understand the options in **xaringan**.
+
+.footnote[[*] It is different with Pandoc's Markdown! It is limited but should be enough for presentation purposes. Come on... You do not need a slide for the Table of Contents! Well, the Markdown support in remark.js [may be improved](https://github.com/gnab/remark/issues/142) in the future.]
+
+---
+background-image: url(https://github.com/yihui/xaringan/releases/download/v0.0.2/karl-moustache.jpg)
+background-size: cover
+class: center, bottom, inverse
+
+# I was so happy to have discovered remark.js!
+
+---
+class: inverse, middle, center
+
+# Using xaringan
+
+---
+
+# xaringan
+
+Provides an R Markdown output format `xaringan::moon_reader` as a wrapper for remark.js, and you can use it in the YAML metadata, e.g.
+
+```yaml
+---
+title: "A Cool Presentation"
+output:
+  xaringan::moon_reader:
+    yolo: true
+    nature:
+      autoplay: 30000
+---
+```
+
+See the help page `?xaringan::moon_reader` for all possible options that you can use.
+
+---
+
+# remark.js vs xaringan
+
+Some differences between using remark.js (left) and using **xaringan** (right):
+
+.pull-left[
+1. Start with a boilerplate HTML file;
+
+1. Plain Markdown;
+
+1. Write JavaScript to autoplay slides;
+
+1. Manually configure MathJax;
+
+1. Highlight code with `*`;
+
+1. Edit Markdown source and refresh browser to see updated slides;
+]
+
+.pull-right[
+1. Start with an R Markdown document;
+
+1. R Markdown (can embed R/other code chunks);
+
+1. Provide an option `autoplay`;
+
+1. MathJax just works;&lt;sup&gt;*&lt;/sup&gt;
+
+1. Highlight code with `{{}}`;
+
+1. The RStudio addin "Infinite Moon Reader" automatically refreshes slides on changes;
+]
+
+.footnote[[*] Not really. See next page.]
+
+---
+
+# Math Expressions
+
+You can write LaTeX math expressions inside a pair of dollar signs, e.g. &amp;#36;\alpha+\beta$ renders `\(\alpha+\beta\)`. You can use the display style with double dollar signs:
+
+```
+$$\bar{X}=\frac{1}{n}\sum_{i=1}^nX_i$$
+```
+
+`$$\bar{X}=\frac{1}{n}\sum_{i=1}^nX_i$$`
+
+Limitations:
+
+1. The source code of a LaTeX math expression must be in one line, unless it is inside a pair of double dollar signs, in which case the starting `$$` must appear in the very beginning of a line, followed immediately by a non-space character, and the ending `$$` must be at the end of a line, led by a non-space character;
+
+1. There should not be spaces after the opening `$` or before the closing `$`.
+
+1. Math does not work on the title slide (see [#61](https://github.com/yihui/xaringan/issues/61) for a workaround).
+
+---
+
+# R Code
+
+
+``` r
+# a boring regression
+fit = lm(dist ~ 1 + speed, data = cars)
+coef(summary(fit))
+```
+
+```
+#               Estimate Std. Error   t value     Pr(&gt;|t|)
+# (Intercept) -17.579095  6.7584402 -2.601058 1.231882e-02
+# speed         3.932409  0.4155128  9.463990 1.489836e-12
+```
+
+``` r
+dojutsu = c('地爆天星', '天照', '加具土命', '神威', '須佐能乎', '無限月読')
+grep('天', dojutsu, value = TRUE)
+```
+
+```
+# [1] "地爆天星" "天照"
+```
+
+---
+
+# R Plots
+
+
+``` r
+par(mar = c(4, 4, 1, .1))
+plot(cars, pch = 19, col = 'darkgray', las = 1)
+abline(fit, lwd = 2)
+```
+
+![](IDK_files/figure-html/cars-1.svg)&lt;!-- --&gt;
+
+---
+
+# Tables
+
+If you want to generate a table, make sure it is in the HTML format (instead of Markdown or other formats), e.g.,
+
+
+``` r
+knitr::kable(head(iris), format = 'html')
+```
+
+&lt;table&gt;
+ &lt;thead&gt;
+  &lt;tr&gt;
+   &lt;th style="text-align:right;"&gt; Sepal.Length &lt;/th&gt;
+   &lt;th style="text-align:right;"&gt; Sepal.Width &lt;/th&gt;
+   &lt;th style="text-align:right;"&gt; Petal.Length &lt;/th&gt;
+   &lt;th style="text-align:right;"&gt; Petal.Width &lt;/th&gt;
+   &lt;th style="text-align:left;"&gt; Species &lt;/th&gt;
+  &lt;/tr&gt;
+ &lt;/thead&gt;
+&lt;tbody&gt;
+  &lt;tr&gt;
+   &lt;td style="text-align:right;"&gt; 5.1 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 3.5 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 1.4 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 0.2 &lt;/td&gt;
+   &lt;td style="text-align:left;"&gt; setosa &lt;/td&gt;
+  &lt;/tr&gt;
+  &lt;tr&gt;
+   &lt;td style="text-align:right;"&gt; 4.9 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 3.0 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 1.4 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 0.2 &lt;/td&gt;
+   &lt;td style="text-align:left;"&gt; setosa &lt;/td&gt;
+  &lt;/tr&gt;
+  &lt;tr&gt;
+   &lt;td style="text-align:right;"&gt; 4.7 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 3.2 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 1.3 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 0.2 &lt;/td&gt;
+   &lt;td style="text-align:left;"&gt; setosa &lt;/td&gt;
+  &lt;/tr&gt;
+  &lt;tr&gt;
+   &lt;td style="text-align:right;"&gt; 4.6 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 3.1 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 1.5 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 0.2 &lt;/td&gt;
+   &lt;td style="text-align:left;"&gt; setosa &lt;/td&gt;
+  &lt;/tr&gt;
+  &lt;tr&gt;
+   &lt;td style="text-align:right;"&gt; 5.0 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 3.6 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 1.4 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 0.2 &lt;/td&gt;
+   &lt;td style="text-align:left;"&gt; setosa &lt;/td&gt;
+  &lt;/tr&gt;
+  &lt;tr&gt;
+   &lt;td style="text-align:right;"&gt; 5.4 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 3.9 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 1.7 &lt;/td&gt;
+   &lt;td style="text-align:right;"&gt; 0.4 &lt;/td&gt;
+   &lt;td style="text-align:left;"&gt; setosa &lt;/td&gt;
+  &lt;/tr&gt;
+&lt;/tbody&gt;
+&lt;/table&gt;
+
+---
+
+# HTML Widgets
+
+I have not thoroughly tested HTML widgets against **xaringan**. Some may work well, and some may not. It is a little tricky.
+
+Similarly, the Shiny mode (`runtime: shiny`) does not work. I might get these issues fixed in the future, but these are not of high priority to me. I never turn my presentation into a Shiny app. When I need to demonstrate more complicated examples, I just launch them separately. It is convenient to share slides with other people when they are plain HTML/JS applications.
+
+See the next page for two HTML widgets.
+
+---
+
+
+``` r
+library(leaflet)
+leaflet() %&gt;% addTiles() %&gt;% setView(-93.65, 42.0285, zoom = 17)
+```
+
+<div class="leaflet html-widget html-fill-item" id="htmlwidget-a8bf9e69ddd22f76ce7f" style="width:100%;height:432px;"></div>
+<script type="application/json" data-for="htmlwidget-a8bf9e69ddd22f76ce7f">{"x":{"options":{"crs":{"crsClass":"L.CRS.EPSG3857","code":null,"proj4def":null,"projectedBounds":null,"options":{}}},"calls":[{"method":"addTiles","args":["https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png",null,null,{"minZoom":0,"maxZoom":18,"tileSize":256,"subdomains":"abc","errorTileUrl":"","tms":false,"noWrap":false,"zoomOffset":0,"zoomReverse":false,"opacity":1,"zIndex":1,"detectRetina":false,"attribution":"&copy; <a href=\"https://openstreetmap.org/copyright/\">OpenStreetMap<\/a>,  <a href=\"https://opendatacommons.org/licenses/odbl/\">ODbL<\/a>"}]}],"setView":[[42.0285,-93.65000000000001],17,[]]},"evals":[],"jsHooks":[]}</script>
+
+---
+
+
+``` r
+DT::datatable(
+  head(iris, 10),
+  fillContainer = FALSE, options = list(pageLength = 8)
+)
+```
+
+<div class="datatables html-widget html-fill-item" id="htmlwidget-ce73e56e0ac472215fbf" style="width:100%;height:auto;"></div>
+<script type="application/json" data-for="htmlwidget-ce73e56e0ac472215fbf">{"x":{"filter":"none","vertical":false,"fillContainer":false,"data":[["1","2","3","4","5","6","7","8","9","10"],[5.1,4.9,4.7,4.6,5,5.4,4.6,5,4.4,4.9],[3.5,3,3.2,3.1,3.6,3.9,3.4,3.4,2.9,3.1],[1.4,1.4,1.3,1.5,1.4,1.7,1.4,1.5,1.4,1.5],[0.2,0.2,0.2,0.2,0.2,0.4,0.3,0.2,0.2,0.1],["setosa","setosa","setosa","setosa","setosa","setosa","setosa","setosa","setosa","setosa"]],"container":"<table class=\"display\">\n  <thead>\n    <tr>\n      <th> <\/th>\n      <th>Sepal.Length<\/th>\n      <th>Sepal.Width<\/th>\n      <th>Petal.Length<\/th>\n      <th>Petal.Width<\/th>\n      <th>Species<\/th>\n    <\/tr>\n  <\/thead>\n<\/table>","options":{"pageLength":8,"columnDefs":[{"className":"dt-right","targets":[1,2,3,4]},{"orderable":false,"targets":0},{"name":" ","targets":0},{"name":"Sepal.Length","targets":1},{"name":"Sepal.Width","targets":2},{"name":"Petal.Length","targets":3},{"name":"Petal.Width","targets":4},{"name":"Species","targets":5}],"order":[],"autoWidth":false,"orderClasses":false,"lengthMenu":[8,10,25,50,100]}},"evals":[],"jsHooks":[]}</script>
+
+---
+
+# Some Tips
+
+- Do not forget to try the `yolo` option of `xaringan::moon_reader`.
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        yolo: true
+    ```
+
+---
+
+# Some Tips
+
+- Slides can be automatically played if you set the `autoplay` option under `nature`, e.g. go to the next slide every 30 seconds in a lightning talk:
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        nature:
+          autoplay: 30000
+    ```
+
+- If you want to restart the play after it reaches the last slide, you may set the sub-option `loop` to TRUE, e.g.,
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        nature:
+          autoplay:
+            interval: 30000
+            loop: true
+    ```
+
+---
+
+# Some Tips
+
+- A countdown timer can be added to every page of the slides using the `countdown` option under `nature`, e.g. if you want to spend one minute on every page when you give the talk, you can set:
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        nature:
+          countdown: 60000
+    ```
+
+    Then you will see a timer counting down from `01:00`, to `00:59`, `00:58`, ... When the time is out, the timer will continue but the time turns red.
+    
+---
+
+# Some Tips
+
+- The title slide is created automatically by **xaringan**, but it is just another remark.js slide added before your other slides.
+
+    The title slide is set to `class: center, middle, inverse, title-slide` by default. You can change the classes applied to the title slide with the `titleSlideClass` option of `nature` (`title-slide` is always applied).
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        nature:
+          titleSlideClass: [top, left, inverse]
+    ```
+    
+--
+
+- If you'd like to create your own title slide, disable **xaringan**'s title slide with the `seal = FALSE` option of `moon_reader`.
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        seal: false
+    ```
+
+---
+
+# Some Tips
+
+- There are several ways to build incremental slides. See [this presentation](https://slides.yihui.org/xaringan/incremental.html) for examples.
+
+- The option `highlightLines: true` of `nature` will highlight code lines that start with `*`, or are wrapped in `{{ }}`, or have trailing comments `#&lt;&lt;`;
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        nature:
+          highlightLines: true
+    ```
+
+    See examples on the next page.
+
+---
+
+# Some Tips
+
+
+.pull-left[
+An example using a leading `*`:
+
+    ```r
+    if (TRUE) {
+    ** message("Very important!")
+    }
+    ```
+Output:
+```r
+if (TRUE) {
+* message("Very important!")
+}
+```
+
+This is invalid R code, so it is a plain fenced code block that is not executed.
+]
+
+.pull-right[
+An example using `{{}}`:
+
+````
+```{r tidy=FALSE}
+if (TRUE) {
+*{{ message("Very important!") }}
+}
+```
+````
+Output:
+
+``` r
+if (TRUE) {
+* message("Very important!") 
+}
+```
+
+```
+## Very important!
+```
+
+It is valid R code so you can run it. Note that `{{}}` can wrap an R expression of multiple lines.
+]
+
+---
+
+# Some Tips
+
+An example of using the trailing comment `#&lt;&lt;` to highlight lines:
+
+````markdown
+```{r tidy=FALSE}
+library(ggplot2)
+ggplot(mtcars) + 
+  aes(mpg, disp) + 
+  geom_point() +   #&lt;&lt;
+  geom_smooth()    #&lt;&lt;
+```
+````
+
+Output:
+
+
+``` r
+library(ggplot2)
+ggplot(mtcars) + 
+  aes(mpg, disp) + 
+* geom_point() +
+* geom_smooth()
+```
+
+---
+
+# Some Tips
+
+When you enable line-highlighting, you can also use the chunk option `highlight.output` to highlight specific lines of the text output from a code chunk. For example, `highlight.output = TRUE` means highlighting all lines, and `highlight.output = c(1, 3)` means highlighting the first and third line.
+
+````md
+```{r, highlight.output=c(1, 3)}
+head(iris)
+```
+````
+
+
+```
+*##   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
+## 1          5.1         3.5          1.4         0.2  setosa
+*## 2          4.9         3.0          1.4         0.2  setosa
+## 3          4.7         3.2          1.3         0.2  setosa
+## 4          4.6         3.1          1.5         0.2  setosa
+## 5          5.0         3.6          1.4         0.2  setosa
+## 6          5.4         3.9          1.7         0.4  setosa
+```
+
+Question: what does `highlight.output = c(TRUE, FALSE)` mean? (Hint: think about R's recycling of vectors)
+
+---
+
+# Some Tips
+
+- To make slides work offline, you need to download a copy of remark.js in advance, because **xaringan** uses the online version by default (see the help page `?xaringan::moon_reader`).
+
+- You can use `xaringan::summon_remark()` to download the latest or a specified version of remark.js. By default, it is downloaded to `libs/remark-latest.min.js`.
+
+- Then change the `chakra` option in YAML to point to this file, e.g.
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        chakra: libs/remark-latest.min.js
+    ```
+
+- If you used Google fonts in slides (the default theme uses _Yanone Kaffeesatz_, _Droid Serif_, and _Source Code Pro_), they won't work offline unless you download or install them locally. The Heroku app [google-webfonts-helper](https://google-webfonts-helper.herokuapp.com/fonts) can help you download fonts and generate the necessary CSS.
+
+---
+
+# Macros
+
+- remark.js [allows users to define custom macros](https://github.com/yihui/xaringan/issues/80) (JS functions) that can be applied to Markdown text using the syntax `![:macroName arg1, arg2, ...]` or `![:macroName arg1, arg2, ...](this)`. For example, before remark.js initializes the slides, you can define a macro named `scale`:
+
+    ```js
+    remark.macros.scale = function (percentage) {
+      var url = this;
+      return '&lt;img src="' + url + '" style="width: ' + percentage + '" /&gt;';
+    };
+    ```
+
+    Then the Markdown text
+
+    ```markdown
+    ![:scale 50%](image.jpg)
+    ```
+
+    will be translated to
+    
+    ```html
+    &lt;img src="image.jpg" style="width: 50%" /&gt;
+    ```
+
+---
+
+# Macros (continued)
+
+- To insert macros in **xaringan** slides, you can use the option `beforeInit` under the option `nature`, e.g.,
+
+    ```yaml
+    output:
+      xaringan::moon_reader:
+        nature:
+          beforeInit: "macros.js"
+    ```
+
+    You save your remark.js macros in the file `macros.js`.
+
+- The `beforeInit` option can be used to insert arbitrary JS code before `remark.create()`. Inserting macros is just one of its possible applications.
+
+---
+
+# CSS
+
+Among all options in `xaringan::moon_reader`, the most challenging but perhaps also the most rewarding one is `css`, because it allows you to customize the appearance of your slides using any CSS rules or hacks you know.
+
+You can see the default CSS file [here](https://github.com/yihui/xaringan/blob/master/inst/rmarkdown/templates/xaringan/resources/default.css). You can completely replace it with your own CSS files, or define new rules to override the default. See the help page `?xaringan::moon_reader` for more information.
+
+---
+
+# CSS
+
+For example, suppose you want to change the font for code from the default "Source Code Pro" to "Ubuntu Mono". You can create a CSS file named, say, `ubuntu-mono.css`:
+
+```css
+@import url(https://fonts.googleapis.com/css?family=Ubuntu+Mono:400,700,400italic);
+
+.remark-code, .remark-inline-code { font-family: 'Ubuntu Mono'; }
+```
+
+Then set the `css` option in the YAML metadata:
+
+```yaml
+output:
+  xaringan::moon_reader:
+    css: ["default", "ubuntu-mono.css"]
+```
+
+Here I assume `ubuntu-mono.css` is under the same directory as your Rmd.
+
+See [yihui/xaringan#83](https://github.com/yihui/xaringan/issues/83) for an example of using the [Fira Code](https://github.com/tonsky/FiraCode) font, which supports ligatures in program code.
+
+---
+
+# CSS (with Sass)
+
+**xaringan** also supports Sass support via **rmarkdown**. Suppose you want to use the same color for different elements, e.g., first heading and bold text. You can create a `.scss` file, say `mytheme.scss`, using the [sass](https://sass-lang.com/) syntax with variables:
+
+```scss
+$mycolor: #ff0000; 
+.remark-slide-content &gt; h1 { color: $mycolor; }
+.remark-slide-content strong { color: $mycolor; }
+```
+
+Then set the `css` option in the YAML metadata using this file placed under the same directory as your Rmd:
+
+```yaml
+output:
+  xaringan::moon_reader:
+    css: ["default", "mytheme.scss"]
+```
+
+This requires **rmarkdown** &gt;= 2.8 and the [**sass**](https://rstudio.github.io/sass/) package. You can learn more about **rmarkdown** and **sass** support in [this blog post](https://blog.rstudio.com/2021/04/15/2021-spring-rmd-news/#sass-and-scss-support-for-html-based-output) and in [**sass** overview vignette](https://rstudio.github.io/sass/articles/sass.html).
+
+---
+
+# Themes
+
+Don't want to learn CSS? Okay, you can use some user-contributed themes. A theme typically consists of two CSS files `foo.css` and `foo-fonts.css`, where `foo` is the theme name. Below are some existing themes:
+
+
+``` r
+names(xaringan:::list_css())
+```
+
+```
+##  [1] "chocolate-fonts"  "chocolate"        "default-fonts"   
+##  [4] "default"          "duke-blue"        "fc-fonts"        
+##  [7] "fc"               "glasgow_template" "hygge-duke"      
+## [10] "hygge"            "ki-fonts"         "ki"              
+## [13] "kunoichi"         "lucy-fonts"       "lucy"            
+## [16] "metropolis-fonts" "metropolis"       "middlebury-fonts"
+## [19] "middlebury"       "nhsr-fonts"       "nhsr"            
+## [22] "ninjutsu"         "rladies-fonts"    "rladies"         
+## [25] "robot-fonts"      "robot"            "rutgers-fonts"   
+## [28] "rutgers"          "shinobi"          "tamu-fonts"      
+## [31] "tamu"             "uio-fonts"        "uio"             
+## [34] "uo-fonts"         "uo"               "uol-fonts"       
+## [37] "uol"              "useR-fonts"       "useR"            
+## [40] "uwm-fonts"        "uwm"              "wic-fonts"       
+## [43] "wic"
+```
+
+---
+
+# Themes
+
+To use a theme, you can specify the `css` option as an array of CSS filenames (without the `.css` extensions), e.g.,
+
+```yaml
+output:
+  xaringan::moon_reader:
+    css: [default, metropolis, metropolis-fonts]
+```
+
+If you want to contribute a theme to **xaringan**, please read [this blog post](https://yihui.org/en/2017/10/xaringan-themes).
+
+---
+class: inverse, middle, center
+background-image: url(https://upload.wikimedia.org/wikipedia/commons/3/39/Naruto_Shiki_Fujin.svg)
+background-size: contain
+
+# Naruto
+
+---
+background-image: url(https://upload.wikimedia.org/wikipedia/commons/b/be/Sharingan_triple.svg)
+background-size: 100px
+background-position: 90% 8%
+
+# Sharingan
+
+The R package name **xaringan** was derived&lt;sup&gt;1&lt;/sup&gt; from **Sharingan**, a dōjutsu in the Japanese anime _Naruto_ with two abilities:
+
+- the "Eye of Insight"
+
+- the "Eye of Hypnotism"
+
+I think a presentation is basically a way to communicate insights to the audience, and a great presentation may even "hypnotize" the audience.&lt;sup&gt;2,3&lt;/sup&gt;
+
+.footnote[
+[1] In Chinese, the pronounciation of _X_ is _Sh_ /ʃ/ (as in _shrimp_). Now you should have a better idea of how to pronounce my last name _Xie_.
+
+[2] By comparison, bad presentations only put the audience to sleep.
+
+[3] Personally I find that setting background images for slides is a killer feature of remark.js. It is an effective way to bring visual impact into your presentations.
+]
+
+---
+
+# Naruto terminology
+
+The **xaringan** package borrowed a few terms from Naruto, such as
+
+- [Sharingan](https://naruto.fandom.com/wiki/Sharingan) (写輪眼; the package name)
+
+- The [moon reader](https://naruto.fandom.com/wiki/Moon_Reader) (月読; an attractive R Markdown output format)
+
+- [Chakra](https://naruto.fandom.com/wiki/Chakra) (查克拉; the path to the remark.js library, which is the power to drive the presentation)
+
+- [Nature transformation](https://naruto.fandom.com/wiki/Nature_Transformation) (性質変化; transform the chakra by setting different options)
+
+- The [infinite moon reader](https://naruto.fandom.com/wiki/Infinite_Tsukuyomi) (無限月読; start a local web server to continuously serve your slides)
+
+- The [summoning technique](https://naruto.fandom.com/wiki/Summoning_Technique) (download remark.js from the web)
+
+You can click the links to know more about them if you want. The jutsu "Moon Reader" may seem a little evil, but that does not mean your slides are evil.
+
+---
+
+class: center
+
+# Hand seals (印)
+
+Press `h` or `?` to see the possible ninjutsu you can use in remark.js.
+
+![](https://upload.wikimedia.org/wikipedia/commons/7/7e/Mudra-Naruto-KageBunshin.svg)
+
+---
+
+class: center, middle
+
+# Thanks!
+
+Slides created via the R package [**xaringan**](https://github.com/yihui/xaringan).
+
+The chakra comes from [remark.js](https://remarkjs.com), [**knitr**](https://yihui.org/knitr/), and [R Markdown](https://rmarkdown.rstudio.com).
+    </textarea>
+<style data-target="print-only">@media screen {.remark-slide-container{display:block;}.remark-slide-scaler{box-shadow:none;}}</style>
+<script src="https://remarkjs.com/downloads/remark-latest.min.js"></script>
+<script>var slideshow = remark.create({
+  "highlightStyle": "github",
+  "highlightLines": true,
+  "countIncrementalSlides": false
+});
+if (window.HTMLWidgets) slideshow.on('afterShowSlide', function (slide) {
+  window.dispatchEvent(new Event('resize'));
+});
+(function(d) {
+  var s = d.createElement("style"), r = d.querySelector(".remark-slide-scaler");
+  if (!r) return;
+  s.type = "text/css"; s.innerHTML = "@page {size: " + r.style.width + " " + r.style.height +"; }";
+  d.head.appendChild(s);
+})(document);
+
+(function(d) {
+  var el = d.getElementsByClassName("remark-slides-area");
+  if (!el) return;
+  var slide, slides = slideshow.getSlides(), els = el[0].children;
+  for (var i = 1; i < slides.length; i++) {
+    slide = slides[i];
+    if (slide.properties.continued === "true" || slide.properties.count === "false") {
+      els[i - 1].className += ' has-continuation';
+    }
+  }
+  var s = d.createElement("style");
+  s.type = "text/css"; s.innerHTML = "@media print { .has-continuation { display: none; } }";
+  d.head.appendChild(s);
+})(document);
+// delete the temporary CSS (for displaying all slides initially) when the user
+// starts to view slides
+(function() {
+  var deleted = false;
+  slideshow.on('beforeShowSlide', function(slide) {
+    if (deleted) return;
+    var sheets = document.styleSheets, node;
+    for (var i = 0; i < sheets.length; i++) {
+      node = sheets[i].ownerNode;
+      if (node.dataset["target"] !== "print-only") continue;
+      node.parentNode.removeChild(node);
+    }
+    deleted = true;
+  });
+})();
+// add `data-at-shortcutkeys` attribute to <body> to resolve conflicts with JAWS
+// screen reader (see PR #262)
+(function(d) {
+  let res = {};
+  d.querySelectorAll('.remark-help-content table tr').forEach(tr => {
+    const t = tr.querySelector('td:nth-child(2)').innerText;
+    tr.querySelectorAll('td:first-child .key').forEach(key => {
+      const k = key.innerText;
+      if (/^[a-z]$/.test(k)) res[k] = t;  // must be a single letter (key)
+    });
+  });
+  d.body.setAttribute('data-at-shortcutkeys', JSON.stringify(res));
+})(document);
+(function() {
+  "use strict"
+  // Replace <script> tags in slides area to make them executable
+  var scripts = document.querySelectorAll(
+    '.remark-slides-area .remark-slide-container script'
+  );
+  if (!scripts.length) return;
+  for (var i = 0; i < scripts.length; i++) {
+    var s = document.createElement('script');
+    var code = document.createTextNode(scripts[i].textContent);
+    s.appendChild(code);
+    var scriptAttrs = scripts[i].attributes;
+    for (var j = 0; j < scriptAttrs.length; j++) {
+      s.setAttribute(scriptAttrs[j].name, scriptAttrs[j].value);
+    }
+    scripts[i].parentElement.replaceChild(s, scripts[i]);
+  }
+})();
+(function() {
+  var links = document.getElementsByTagName('a');
+  for (var i = 0; i < links.length; i++) {
+    if (/^(https?:)?\/\//.test(links[i].getAttribute('href'))) {
+      links[i].target = '_blank';
+    }
+  }
+})();
+// adds .remark-code-has-line-highlighted class to <pre> parent elements
+// of code chunks containing highlighted lines with class .remark-code-line-highlighted
+(function(d) {
+  const hlines = d.querySelectorAll('.remark-code-line-highlighted');
+  const preParents = [];
+  const findPreParent = function(line, p = 0) {
+    if (p > 1) return null; // traverse up no further than grandparent
+    const el = line.parentElement;
+    return el.tagName === "PRE" ? el : findPreParent(el, ++p);
+  };
+
+  for (let line of hlines) {
+    let pre = findPreParent(line);
+    if (pre && !preParents.includes(pre)) preParents.push(pre);
+  }
+  preParents.forEach(p => p.classList.add("remark-code-has-line-highlighted"));
+})(document);</script>
+
+<script>
+slideshow._releaseMath = function(el) {
+  var i, text, code, codes = el.getElementsByTagName('code');
+  for (i = 0; i < codes.length;) {
+    code = codes[i];
+    if (code.parentNode.tagName !== 'PRE' && code.childElementCount === 0) {
+      text = code.textContent;
+      if (/^\\\((.|\s)+\\\)$/.test(text) || /^\\\[(.|\s)+\\\]$/.test(text) ||
+          /^\$\$(.|\s)+\$\$$/.test(text) ||
+          /^\\begin\{([^}]+)\}(.|\s)+\\end\{[^}]+\}$/.test(text)) {
+        code.outerHTML = code.innerHTML;  // remove <code></code>
+        continue;
+      }
+    }
+    i++;
+  }
+};
+slideshow._releaseMath(document);
+</script>
+<!-- dynamically load mathjax for compatibility with self-contained -->
+<script>
+(function () {
+  var script = document.createElement('script');
+  script.type = 'text/javascript';
+  script.src  = 'https://mathjax.rstudio.com/latest/MathJax.js?config=TeX-MML-AM_CHTML';
+  if (location.protocol !== 'file:' && /^https?:/.test(script.src))
+    script.src  = script.src.replace(/^https?:/, '');
+  document.getElementsByTagName('head')[0].appendChild(script);
+})();
+</script>
+  </body>
+</html>
