PButton startBtn, clearBtn ;
PFont myFont;
float t1, t2;
float x, y, cre, cim;
int j = 0;
int k =0;
int period = 20;
float sc = 150.0;
float modsqr;
float [] cA2 = {0.0, 0.0};
color[] colA = {#0000FF, #2323DC, #4646B9, #696996, #8C8C73, #AFAF50,
                 #D2D22D, #F5F50A, #FFFF00};
                 
void setup(){
size(400, 500); 
startBtn = new PButton(320,450,60,20, "Start");
clearBtn = new PButton(250,450,60,20, "Clear");   
myFont = loadFont("sansserif.bold-14.vlw");
 fill(#000000);
 textFont(myFont);
noLoop();
 }
 
void draw() { 
 if(startBtn.over())
     runthis();
 if(clearBtn.over())
     clearthis();
} 
 
 float[] mandel(float x, float y, float pre, float pim)
  { float[] result = {pre+(x*x-y*y), 2*x*y + pim};
  return (result);
  }
  
 //event handler
void mouseReleased () 
{ 
  if(startBtn.over())startBtnAction();
  if(clearBtn.over()) redraw();
}
 
 
void  startBtnAction(){
 j= 0; k = 0;
 t1 = millis();
 redraw();
} 

void clearthis(){
color c = get(248, 450);
noStroke();
fill(c);
rect(0,0, 400, 449);

noLoop();
}

void runthis(){
while( j <201){
for(int i=0; i<400; i++)  
  {   
      cre = (i-300)/sc;
      cim = (j-200)/sc;
      x = 0.0;
      y = 0.0;
      modsqr = x*x + y*y;
      stroke(#000000);
 		while ((k<period) && (modsqr<4)) {
			cA2 = mandel(x, y, cre, cim);
			x = cA2[0];
			y = cA2[1];
			modsqr = x*x+y*y;
			k++;
		}
		if (k<18) {
                        stroke(colA[floor(k/2)]);
		}
		k = 0;
       point(i,j); 
       point(i, 400-j); }
  j++;}
 t2 = millis();
 t2 -= t1;
 t2 /= 1000;
 fill(#000000);
 text("Elapsed time =   " + str(t2) + " secs", 10, 430);
 noLoop();
}

class PButton {
	float x, y;
	float w, h;
        String label = ""; 
        PFont myFont;
	PButton( float x, float y , float w, float h, String lab1) {
		this.x = x;
		this.y = y;
		this.w = w;
                this.h = h;
                label = lab1;
                initBtn();
	}

    void initBtn(){
    myFont = loadFont("sansserif.bold-14.vlw");
    textFont(myFont);
     fill(#888888);
     rect(x,y, w,h);
     fill(#000000);
    text (label, x+12, y+14);
    } 

    boolean over(){ 
       boolean result = false; 
       if (mouseX>x && mouseX<x+w && mouseY>y && mouseY<y+w) 
       result = true;
       return result;
         }
    }// End of PButton class