grid.css

full_width = 80
columns = 12
gutter = 1

.container
  width unit(full_width, '%')
  margin auto
  overflow hidden

div[class^="grid_"]
  display inline
  float left
  margin-left unit(gutter, '%')
  margin-right unit(gutter, '%')

for col in 1..columns
  .grid_{col}
    width unit((col / columns - gutter / 100 * 2) * 100, '%')

@media screen and (max-width: 480px)
  div[class^="grid_"]
    float none
    display block
    width 100%
    margin 0