font-families = "Lucida Grande", Arial
main-width = 80%
main-color = #fff
sidebar-width = main-width / 2

// Mixins can use conditionals
// to supply defaults
unless font-families is defined
  font-families = 'WAHOO'

// Alternatively we may use ?=
font-families ?= 'WAHOO'

body
  size = 12px
  font size font-families, sans-serif
  color main-color

#wrapper
  width main-width

.sidebar
  width sidebar-width