Dramatically improved TL;DR section

_sass/base/_base.scss

@@ -40,6 +40,20 @@ a,
   }
 }
 
+/**
+ * Prevent back-links in TL;DR lists from being underlined
+ */
+:not(.toc) > h1:last-of-type ~ ul [href^='#'] {
+  text-decoration: none;
+  opacity: 0.5;
+  color: $dark-pink;
+  transition: opacity 0.15s ease-out;
+
+  @include on-event {
+    opacity: 1;
+  }
+}
+
 /**
  * Inline code
  * 1. Make the text slightly smaller as the font looks bigger

en/_tldr.md

@@ -1,26 +1,76 @@
 
-# Too Long; Didn't read
-
-To sum up, we want:
-
-* Two (2) spaces indents, no tabs;
-* 80-characters wide lines;
-* Properly written multi-line CSS;
-* Meaningful use of whitespaces;
-* Quoted strings (single quotes) & URLs;
-* No trailing 0, mandatory leading 0;
-* Calculations wrapped in parentheses;
-* No magic numbers;
-* Colors expressed HSL > RGB > hexadecimal (lowercase and shortened), no keyword;
-* Lists separated with commas;
-* No trailing comma in lists (since they are inlined);
-* Trailing comma in maps;
-* No selector nesting except for pseudo-classes and pseudo-elements;
-* Hyphen-delimited naming;
-* Extensive comments;
-* SassDoc-powered API comments;
-* Limited usage of `@extend`;
-* Simple mixins;
-* As few loops as possible, no `@while`;
-* Reduced number of dependencies;
-* Meaningful use of warnings and errors.
+# Too Long; Didn’t read
+
+These guidelines are quite long and sometimes it is good to have them summed up in a shorter version. Below is this summary.
+
+## Key principles
+
+* Having a styleguide is all about **consistency**. If you disagree with some rules from Sass Guidelines, fair enough as long as you are consistent. [↩](#why-a-styleguide)
+* Sass should be kept as simple as it can be. Avoid building complex systems unless absolutely necessary. [↩](#key-principles)
+* Keep in mind that sometimes *KISS* (Keep It Simple, Stupid) is better than *DRY* (Don’t Repeat Yourself). [↩](#key-principles)
+
+## Syntax & formatting
+
+* An indentation is made of two (2) spaces, no tabs. [↩](#syntax--formatting)
+* Lines should be, as much as possible, shorter than 80 characters. Feel free to split them into several lines when necessary. [↩](#syntax--formatting)
+* CSS should be properly written, possibly following the [CSS Guidelines](http://cssguidelin.es) from Harry Roberts. [↩](#syntax--formatting)
+* Whitespace is free, use it to separate items, rules and declarations. Do not hesitate to leave empty lines, it never hurts. [↩](#syntax--formatting)
+
+### Strings
+
+* Declaring the `@charset` directive on top of the stylesheet is highly recommended. [↩](#encoding)
+* Unless applied as CSS identifiers, strings should be quoted using single quotes. URLs should also be quoted. [↩](#strings-as-css-values)
+
+### Numbers
+
+* Sass makes no distinction between numbers, integers, floats so trailing zeros (0) should be omitted. However, leading zeros (0) help readability and should be added. [↩](#zeros)
+* A zero (0) length should not have a unit. [↩](#units)
+* Units manipulation should be thought as arithmetic operations, not string operations. [↩](#units)
+* In order to improve readability, top-level calculations should be wrapped in parentheses. Also, complex math operations might be splitted into smaller chunks. [↩](#calculations)
+* Magic numbers dramatically hurt code maintainability and should be avoided at all time. When in doubt, extensively explain the questionable value. [↩](#magic-numbers)
+
+### Colors
+
+* Colors should be expressed in HSL when possible, then RGB, then hexadecimal (in a lowercase and shortened form). Color keywords should be avoided. [↩](#color-formats)
+* Prefer `mix(..)` instead of `darken(..)` and `lighten(..)` when lightening or darkening a color. [↩](#lightening-and-darkening-colors)
+
+### Lists
+
+* Unless used as a direct mapping to space-separated CSS values, lists should be separated with commas. [↩](#lists)
+* Wrapping parentheses should also be considered to improve readability. [↩](#lists)
+* Inlined lists should not have a trailing comma, multi-line lists should have it. [↩](#lists)
+
+### Maps
+
+* Maps containing more than a single pair are written on several lines. [↩](#maps)
+* To help maintainability, the last pair of a map should have a trailing comma. [↩](#maps)
+* Map keys that happen to be strings should be quoted as any other string. [↩](#maps)
+
+### Declaration sorting
+
+* The system used for declaration sorting (alphabetical, by type, etc.) doesn’t matter as long as it is consistent. [↩](#declaration-sorting)
+
+### Selector nesting
+
+* Avoid selector nesting when it is not needed (which represents most of the cases). [↩](#selector-nesting)
+* Use selector nesting for pseudo-classes and pseudo-elements. [↩](#selector-nesting)
+* Media queries can also be nested inside their relevant selector. [↩](#selector-nesting)
+
+## Naming conventions
+
+* It is best to stick to CSS naming conventions which are (except a few errors) lowercase and hyphen-delimited. [↩](#naming-conventions)
+
+## Commenting
+
+* CSS is a tricky language; do not hesitate to write very extensive comments about things that look (or are) fishy. [↩](#commenting)
+* For variables, functions, mixins and placeholders establishing a public API, use SassDoc comments. [↩](#documentation)
+
+## Variables
+
+* Do use the `!default` flag for any variable part of a public API that can be safely changed. [↩](#default-flag)
+* Do not use the `!global` flag at root level as it might constitue a violation of Sass syntax in the future. [↩](#global-flag)
+
+## Extend
+
+* Stick to extending placeholders, not existing CSS selectors. [↩](#extend)
+* Extend a placeholder as few times as possible in order to avoid side effets. [↩](#extend)