float r;
float x;
float y;
float theta=360*30;
int multi = 1;
float espessura;

PGraphics offScreen;

void setup() {
    size(900, 720,P2D);
    //strokeWeight(espessura);
    noFill();
    smooth();
    background(0);
    frameRate(120);
    offScreen =  createGraphics(900, 720, P2D);
    offScreen.beginDraw();
    offScreen.background(0);
    offScreen.noFill();
    offScreen.smooth();
    offScreen.endDraw();
    
}


void draw() {  
    offScreen.beginDraw();
    offScreen.strokeWeight(espessura);

  espessura=0.1+7*mouseX/height;

   offScreen.translate(width/2, height/2); // translate to center of screen

    for (int i =0; i< 250; i++) {
      theta=theta+ multi*0.29;
              
      r = 360-theta/30;
        
          //limites para a espiral parar de ser desenhada 
          if (theta < 0 || theta >360*30) {
            multi = multi * -1; //alternando entre inteiro positivo e negativo: +1 -1
            break;
          }
               if (multi > 0) {
                  offScreen.stroke(0,0,0);
                }
                if (multi < 0) {
                  offScreen.stroke(255, 255, 255);
                  //offScreen.strokeWeight(espessura);
                }
               
              
      x =r*cos(radians(theta)); // radians para converter pi em radianos
      y =r*sin(radians(theta));
          
        
       offScreen.point (x, y);    
        
    }
   offScreen.endDraw();
  translate(width/2,height/2);
  pushMatrix();
  rotate(radians(theta));
 //translate(width/2,height/2);
  image(offScreen,-width/2,-height/2); 
 tint(255,60);

  popMatrix();
}