!ninesixty_gutter_width ||= 20px
!ninesixty_grid_width ||= 960px
!ninesixty_columns ||= 12

=grid-container
  margin-left: auto
  margin-right: auto
  width = !ninesixty_grid_width

=grid-width(!n, !cols = !ninesixty_columns, !gutter_width = !ninesixty_gutter_width)
  width = (!ninesixty_grid_width / !cols) * !n - !gutter_width

=grid-unit-base(!gutter_width = !ninesixty_gutter_width)
  display: inline
  float: left
  margin:
    left = !gutter_width / 2
    right = !gutter_width / 2

=grid(!n, !cols = !ninesixty_columns, !gutter_width = !ninesixty_gutter_width)
  +grid-unit-base(!gutter_width)
  +grid-width(!n, !cols, !gutter_width)

=alpha
  margin-left: 0

=omega
  margin-right: 0

=grids(!cols = !ninesixty_columns, !gutter_width = !ninesixty_gutter_width)
  #{enumerate(".grid_",1,!cols)}
    +grid-unit-base
  @for !n from 1 through !cols
    .grid_#{!n}
      +grid-width(!n, !cols, !gutter_width)

=grid-prefix(!n, !cols = !ninesixty_columns)
  padding-left = (!ninesixty_grid_width / !cols) * !n

=grid-prefixes(!cols = !ninesixty_columns)
  @for !n from 1 through !cols - 1
    .prefix_#{!n}
      +grid-prefix(!n, !cols)

=grid-suffix(!n, !cols = !ninesixty_columns)
  padding-right = (!ninesixty_grid_width / !cols) * !n

=grid-suffixes(!cols = !ninesixty_columns)
  @for !n from 1 through !cols - 1
    .suffix_#{!n}
      +grid-suffix(!n, !cols)

=grid-children
  .alpha
    +alpha
  .omega
    +omega

=grid-system(!cols = !ninesixty_columns)
  +grid-container
  +grids(!cols)
  +grid-prefixes(!cols)
  +grid-suffixes(!cols)
  +grid-children