Rotation an object using processing

Processing Coding Questions
4

Consider this code:

float xo;
float angle=0;

void setup() {
  size(800, 600);
  smooth();
  noStroke();
  reset();
}

void reset() {
  angle = 0;
  xo = 0;
}

void draw() {
  background(0);
  translate(width/2, height/2);
  rotate(angle);
  pushMatrix();
  translate(5, -20);
  fill(255, 255, 255);
  rect(xo, 0, 30, 30);
  popMatrix();
  fill (255, 0, 0);
  rect (0, 0, 300, 10);
}

void keyPressed() {
  if (key==CODED) {
    if (keyCode== RIGHT) {
      angle+= radians(1);
    } else if (keyCode== LEFT) {
      angle-= radians(1);
    } else if (keyCode== UP) {
      xo+= 1;
    } else if (keyCode== DOWN) {
      xo-= 1;
    }
  }
  if (key==' ') {
    reset();
  }
}

Notice the complete lack of a y0 variable!