me-triangle( direction, size, face-color, back-color = transparent )
    width: 0
    height: 0
    border: size solid back-color
    if direction == up || direction == down-left || direction == down-right
        border-bottom-color: face-color
    if direction == down || direction == up-left || direction == up-right
        border-top-color: face-color
    if direction == left || direction == down-right || direction == up-right
        border-right-color: face-color
    if direction == right || direction == down-left || direction == up-left
        border-left-color: face-color

triangle = me-triangle unless me-no-conflict