This mixin creates a triangle using the border properties in css. By using the opposite-position function in Compass we can create a triangle with only 1 argument and let the mixin calculate the opposite side.
=caret($point) $opposite: opposite-position($point) border: 100px solid transparent border-#{$opposite}: 100px solid #000 border-#{$point}: 0 height: 0 width: 0 .caret +caret(top)