Kara draws the triangle row by row, walking alternatively from left to right and from right to left:

HEIGHT = 5
currentWidth = 1
left2right = true

HEIGHT.times {
  paintRow (kara, currentWidth)
  gotoNextRow (kara, left2right)
  left2right = ! left2right
  currentWidth = currentWidth + 2
}

paintRow (kara, currentWidth)