1 files changed, 194 insertions, 0 deletions
diff --git a/doc/development/scss_styleguide.md b/doc/development/scss_styleguide.md
new file mode 100644
index 00000000000..6c48c25448b
--- /dev/null
+++ b/doc/development/scss_styleguide.md
@@ -0,0 +1,194 @@
+# SCSS styleguide
+
+This style guide recommends best practices for SCSS to make styles easy to read,
+easy to maintain, and performant for the end-user.
+
+## Rules
+
+### Naming
+
+CSS classes should use the `lowercase-hyphenated` format rather than
+`snake_case` or `camelCase`.
+
+```scss
+// Bad
+.class_name {
+  color: #fff;
+}
+
+// Bad
+.className {
+  color: #fff;
+}
+
+// Good
+.class-name {
+  color: #fff;
+}
+```
+
+### Formatting
+
+You should always use a space before a brace, braces should be on the same
+line, each property should each get its own line, and there should be a space
+between the property and its value.
+
+```scss
+// Bad
+.container-item { 
+  width: 100px; height: 100px;
+  margin-top: 0;
+}
+
+// Bad
+.container-item
+{
+  width: 100px;
+  height: 100px;
+  margin-top: 0;
+}
+
+// Bad
+.container-item{
+  width:100px;
+  height:100px;
+  margin-top:0;
+}
+
+// Good
+.container-item {
+  width: 100px;
+  height: 100px;
+  margin-top: 0;
+}
+```
+
+Note that there is an exception for single-line rulesets, although these are 
+not typically recommended.
+
+```scss
+p { margin: 0; padding: 0; }
+```
+
+### Colors
+
+HEX (hexadecimal) colors short-form should use shortform where possible, and 
+should use lower case letters to differenciate between letters and numbers, e.
+g. `#E3E3E3` vs. `#e3e3e3`.
+
+```scss
+// Bad
+p {
+  color: #ffffff;
+}
+
+// Bad
+p {
+  color: #FFFFFF;
+}
+
+// Good
+p {
+  color: #fff;
+}
+```
+
+### Indentation
+
+Indentation should always use two spaces for each indentation level.
+
+```scss
+// Bad, four spaces
+p {
+    color: #f00;
+}
+
+// Good
+p {
+  color: #f00;
+}
+```
+
+### Semicolons
+
+Always include semicolons after every property. When the stylesheets are 
+minified, the semicolons will be removed automatically.
+
+```scss
+// Bad
+.container-item {
+  width: 100px;
+  height: 100px
+}
+
+// Good
+.container-item {
+  width: 100px;
+  height: 100px;
+}
+```
+
+### Shorthand
+
+The shorthand form should be used for properties that support it.
+
+```scss
+// Bad
+margin: 10px 15px 10px 15px;
+padding: 10px 10px 10px 10px;
+
+// Good
+margin: 10px 15px;
+padding: 10px;
+```
+
+### Zero Units
+
+Omit length units on zero values, they're unnecessary and not including them 
+is slightly more performant.
+
+```scss
+// Bad
+.item-with-padding {
+  padding: 0px;
+}
+
+// Good
+.item-with-padding {
+  padding: 0;
+}
+```
+
+### Selectors with a `js-` Prefix
+Do not use any selector prefixed with `js-` for styling purposes. These 
+selectors are intended for use only with JavaScript to allow for removal or 
+renaming without breaking styling.
+
+## Linting
+
+We use [SCSS Lint][scss-lint] to check for style guide conformity. It uses the 
+ruleset in `.scss-lint.yml`, which is located in the home directory of the 
+project.
+
+To check if any warnings will be produced by your changes, you can run `rake 
+scss_lint` in the GitLab directory. SCSS Lint will also run in GitLab CI to 
+catch any warnings.
+
+If the Rake task is throwing warnings you don't understand, SCSS Lint's 
+documentation includes [a full list of their linters][scss-lint-documentation].
+
+### Fixing issues
+
+If you want to automate changing a large portion of the codebase to conform to 
+the SCSS style guide, you can use [CSSComb][csscomb]. First install
+[Node][node] and [NPM][npm], then run `npm install csscomb -g` to install 
+CSSComb globally (system-wide). Run it in the GitLab directory with 
+`csscomb app/assets/stylesheets` to automatically fix issues with CSS/SCSS.
+
+Note that this won't fix every problem, but it should fix a majority.
+
+[csscomb]: https://github.com/csscomb/csscomb.js
+[node]: https://github.com/nodejs/node
+[npm]: https://www.npmjs.com/
+[scss-lint]: https://github.com/brigade/scss-lint
+[scss-lint-documentation]: https://github.com/brigade/scss-lint/blob/master/lib/scss_lint/linter/README.md