Rotating a square around the Z axis. To get the results you expect, send the rotate function angle parameters that are values between 0 and PI*2 (TWO_PI which is roughly 6.28). If you prefer to think about angles as degrees (0-360), you can use the radians() method to convert your values. For example: scale(radians(90)) is identical to the statement scale(PI/2).

```
angle = 0
jitter = 0
def setup():
size(640, 360)
noStroke()
fill(255)
rectMode(CENTER)
def draw():
background(51)
global jitter
# during even-numbered seconds (0, 2, 4, 6...)
if second() % 2 == 0:
jitter = random(-0.1, 0.1)
global angle
angle = angle + jitter
c = cos(angle)
translate(width / 2, height / 2)
rotate(c)
rect(0, 0, 180, 180)
```