def setup():
    size(600, 600)
    background(0)
    stroke(255)
    drawTree(300, 550, 9)

def drawTree(x, y, depth):
    fork_ang = radians(20)
    base_len = 10
    if depth > 0:
        pushMatrix()
        translate(x, y - baseLen * depth)
        line(0, baseLen * depth, 0, 0)
        rotate(fork_ang)
        drawTree(0, 0, depth - 1)
        rotate(2 * -fork_ang)
        drawTree(0, 0, depth - 1)
        popMatrix()