Line

xPos = 155
canvasSize = 310

def setup():
    size (canvasSize, canvasSize)
    background(200)
    strokeWeight(3)
    stroke(160, 32, 240)

def draw():
    global xPos
    background(200)
    line(xPos, 0, xPos, canvasSize)
    xPos+=1
    if xPos >= canvasSize: xPos = 0