SCSS. Style guide

# SCSS. Style guide

## Formatting
* Four (4) space indents, no tabs.
* 80 character wide columns.

## CSS rules
* Opening brace ({) placement end of line.
* One space before opening brace.
* Closed brace (}) placement on new line.
* Blank line after closed brace.
* No blank line before closed brace.
* One rule in line.
* One space after colon.
* Always semicolor after rule.
* Local variables define before any rules. Separate blank line.
* Call mixins without @content write before all rules.
* Call mixins with @content write after all nested rules.
 
## Order
* Use always alphabetical order for css-rules in selectors.

## Numbers
* Required leading zero before a deciaml value less than one.
* Zero value shold not be unit.
* Calculations must always be enclosed in parentheses.
* Not use magiс numbers (or explain it in comment).

## Naming
### Variables
* Lowercase, hyphen delimiter words.

        $base-font-stack: Arial, sans-serif;

### Constants
* Uppercase, underscore delimiter words.

        $CONST_NAME: 10;

### Classes
For naming of classes using BEM-notation. Example:

        .block__element_modifier
        .super-block__first-element_modifier_value
        .main-menu__item_active
    
In scss-files elements and modifiers define as nested struct. Example:

        .main-menu {
            // ... rules of block
            
            &__item {
                // ... rules for element
                
                &_active {
                    // ... rules for modified element
                }
            }
        }
    
So style of block will be defined in one struct.

## Colors
* Hex colors in lowercase
* Short notation if possible.