Updated TL;DR

en/_tldr.md

@@ -12,15 +12,15 @@ To sum up, we want:
 * Calculations wrapped in parentheses;
 * No magic numbers;
 * Colors expressed HSL > RGB > hexadecimal (lowercase and shortened), no keyword;
-* Lists separated with commas;
+* Lists wrapped in parentheses and 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;
+* Only extend placeholders, and as few times as possible;
+* As simple as possible mixins;
 * As few loops as possible, no `@while`;
 * Reduced number of dependencies;
-* Meaningful use of warnings and errors.
+* Meaningful usage of warnings and errors.