int num = 20;
int current = 0;
int [] x = new int [num];
int [] y = new int [num];
int [] z = new int [num];
int [] a = new int [num];
int x1, y1, x2, y2;


void setup(){
  size(screen.width,screen.height);
  frameRate(30);
  x1 = width/2;
  y1 = height/2;
  for (int i = 0; i < num; i++){
  x[i] = 0;
  y[i] = 0;
  z[i] = 0;
  a[i] = 0;
  }
}

void draw(){
  background(255);
  for (int c = -width; c < width; c += 100){
    for (int b = -height; b < height; b += 100){
  x2 = mouseX;
  y2 = mouseY;
  line(c+x1,b+y1,c+x2,b+y2);
  
  for (int i = 0; i < num; i++){
  line( c+x[i],b+y[i],c+z[i],b+a[i] );
      }
    }
  }
}

void mousePressed(){
  x[current]= x1 ;
  y[current]= y1;
  z[current]= mouseX ;
  a[current]= mouseY ;
  current++; 
  if (current >= num){
    current = 0;
  }
  x1 = x2;
  y1 = y2;
  
  if (mouseEvent.getClickCount()==2){
    noLoop();
   }  
  }
  
  void keyPressed(){
    if (key == 'n'){
     loop();
    }
  }