int n = 5;
  float[] px = new float[n];
  float[] py = new float[n];
  void setup(){
    float angle = 2 * PI / n; //divide the circle in n sect
    for(int i =0; i< n; i++){
      px[i] = 50. + 30. * sin(angle*i);
      py[i] = 50. + 30. * cos(angle*i);
    }
    rectMode(CENTER);
  }
  void draw (){
    background(200);
    beginShape(POLYGON);
    for(int i = 0; i < n; i++)
      vertex(px[i],py[i]);
    endShape(CLOSE);
    for(int i=0; i<n; i++){
      if(dist(mouseX,mouseY,px[i],py[i])<20)
        stroke(255,0,0);
      else
        stroke(0,0,0);
      rect(px[i],py[i],5,5);
    }
  }
  void mouseDragged(){
    for(int i=0; i<n; i++)
      if(dist(mouseX,mouseY,px[i],py[i])<20){
      px[i] += (mouseX-pmouseX); //push only
      py[i] += (mouseY-pmouseY);
      px[i] = constrain(px[i],5,width-5);
      py[i] = constrain(py[i],5,height-5);
    }
  }