What is your favorite? Pentagon? Hexagon? Heptagon? No? What about the icosagon? The polygon() function created for this example is capable of drawing any regular polygon. Try placing different numbers into the polygon() function calls within draw() to explore. 

def setup():
    size(640, 360)


def draw():
    background(102)

    pushMatrix()
    translate(width * 0.2, height * 0.5)
    rotate(frameCount / 200.0)
    polygon(0, 0, 82, 3)
    popMatrix()

    pushMatrix()
    translate(width * 0.5, height * 0.5)
    rotate(frameCount / 50.0)
    polygon(0, 0, 80, 20)
    popMatrix()

    pushMatrix()
    translate(width * 0.8, height * 0.5)
    rotate(frameCount / -100.0)
    polygon(0, 0, 70, 7)
    popMatrix()


def polygon(x, y, radius, npoints):
    angle = TWO_PI / npoints
    beginShape()
    a = 0
    while a < TWO_PI:
        sx = x + cos(a) * radius
        sy = y + sin(a) * radius
        vertex(sx, sy)
        a += angle
    endShape()