# Style course pages with CSS¶

Main questions:

How to alter the fonts, colors, sizes and spacing of text and images in your course pages.

Topics?

HTML, CSS, Sphinx directives.

What you are supposed to do?

Read the introduction and try it out yourself.

Difficulty:

You need to know some HTML and CSS.

Laboriousness:

A couple of hours to get you started.

The visual outlook and layout of the course pages can be altered. However, changing the aspect of the course pages requires a proper knowledge of HTML and CSS. If you don't know these technologies we advice you not to change the aspects of the course and use the default styles.

## Configuring the CSS file for use¶

First, create a CSS file. In this example it is _static/default.css. If the directory _static does not exist, you must create it. We will come to writing the contents of this file a little bit later.

Second, link to the CSS file in _templates/layout.html. Currently the file looks like this:

{% extends "aplus/layout.html" %}

<!--  MathJax (LaTex math) -->
<script type="text/javascript" async
src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML"
data-aplus>
</script>

<!-- Custom course styles -->
href="{{ pathto('_static/course.css', 1) }}"
type="text/css"
data-aplus />

{% endblock %}


This is a template file for Sphinx. It contains pieces of HTML code that will be inserted on each HTML page when Sphinx compiles the RST files. All commands between tags {% and %} are information for Sphinx: where should this piece of HTML be put? Currently, there are two extra things: we will define that we will include the MathJax JavaScript library from the Internet and use style directives from file _static/course.css inside the main directory of the course.

Third, make sure that file conf.py contains the following line uncommented (without the # character).

html_static_path = ['_static']
templates_path = ['_templates']


This tells Sphinx that there are two special directories. First, there is a static directory, which holds files that are required for the RST compilation but which itself do not change during the compilation. Second, there is the directory for templates, which contain extra HTML code as described.

## Contents of the CSS file¶

After compiling the course, open the files _build/html/introduction/rst.html and _static/course.css in a text editor.

Here is the original admonition block from file introduction/rst.rst:

.. admonition:: Algorithm
:class: meta

An *algorithm* is a finite sequence of unambiguous instructions, which
each can be executed with finite amount of work and which together
compute function

:math:f: I \to O, where
:math:I is the input set,
:math:O is the output set,
:math:\forall i \in I, the algorithm will stop in a way that
:math:o = f(i) \in O


Here is the corresponding result in HTML:

<div class="meta admonition">
<p>An <em>algorithm</em> is a finite sequence of unambiguous instructions, which
each can be executed with finite amount of work and which together
compute function</p>
<p class="last"><span class="math">$$f: I \to O$$</span>, where
<span class="math">$$I$$</span> is the input set,
<span class="math">$$O$$</span> is the output set,
<span class="math">$$\forall i \in I$$</span>, the algorithm will stop in a way that
<span class="math">$$o = f(i) \in O$$</span></p>
</div>


Moreover, our CSS file has some custom settings for the admonition directive:

.admonition, .topic {
min-height: 42px;
margin-bottom: 20px;
border: 1px solid transparent;
margin-left: 0em;
margin-right: 0em;
margin-top: 15px;
}

margin-bottom: 5px;
}

margin-bottom: 0;
}

font-weight: 700;
}

/* some parts cropped out */


As you can see, Sphinx directives produce HTML <div> elements which have a CSS class that corrensponds the name of the Sphinx directive. The different blocks inside directives may have additional classes, like the admonition-title here. You can always compile the RST to HTML, look at the produced HTML code and write corresponding CSS where needed.
Note that if you edit CSS files at directory _static, you must recompile the course, restart A+ and refresh the page in the web browser - the same way when you edit RST files and want to see the result. One can also modify CSS files at directory _build/html/_static and see the results immediately, but that is not wise, because those changes have to be copied to _static before recompiling the course! For faster CSS design, one might want to try the Firefox Developer Edition which has a builtin CSS editor.