円のグラデーションが変化し続ける

/**
* Endless Gradational Circle
*
* @author aa_debdeb
* @date 2015/09/29
*/

float ANGLE_STEP = PI / 64;
float angle = 0.0;

float targetColorR;
float targetColorG;
float targetColorB;

float currentColorR;
float currentColorG;
float currentColorB;

void setup(){
  size(500, 500);
  smooth();
  frameRate(24);
  noStroke();
  background(255);
  setNewTargetColor();
  currentColorR = int(random(256));
  currentColorG = int(random(256));
  currentColorB = int(random(256));
  
}

void setNewTargetColor(){
  targetColorR = int(random(256));
  targetColorG = int(random(256));
  targetColorB = int(random(256));
}

void draw(){ 
  
  if(currentColorR == targetColorR && currentColorG == targetColorG && currentColorB == targetColorB){
    setNewTargetColor();
  }
  
  if(currentColorR < targetColorR){
    currentColorR += 1;
  } else if(currentColorR > targetColorR){
    currentColorR -= 1;
  }
  if(currentColorG < targetColorG){
    currentColorG += 1;
  } else if(currentColorG > targetColorG){
    currentColorG -= 1;
  }
  if(currentColorB < targetColorB){
    currentColorB += 1;
  } else if(currentColorB > targetColorB){
    currentColorB -= 1;
  }
  
  fill(currentColorR, currentColorG, currentColorB);
  arc(width/2, height/2, 300, 300, angle, angle + ANGLE_STEP);
  angle += ANGLE_STEP;
  if(angle >= 2*PI){
    angle -= 2*PI;
  }
}