CSS3 (v0.1.0)

OOCSS is the preferred methodology (Object-Oriented CSS)
Classes should be in recursive alphabetical order
Childs of a class should come after the parent class itself
Only the direct parent class should be written in selector:

.class {
  /* Some styles */
}
.class .childclass {
  /* Some styles */
}

only 2 "parent child" pair can be in selector
Selecting html tags are only allowed when there are no scoped tags:

<div class="class">
  <h1>Heading</h1>
  <p>Paragraph</p>
</div>
<!-- you can select `.class h1` and `.class p` here -->

Ordering for a style group:
1. Class
2. Pseudo-elements
3. Pseudo-classes
Order of pseudo-elements:
1. before
2. after
3. first-line
4. first-letter
5. selection
6. marker
Order of pseudo-classes:
1. hover
2. click
Order of properties:

.class {
  /* Margin and padding */
  /* Display (Flex, grid, etc.) */
  /* Background */
  /* Shadows */
}