http://ludonaut.tumblr.com/post/78889815728

dark_place.pde

// juuuust under 250 for a nicer canvas border.
int randomOffset = 249;
int transparency = 20;

void setup() {
  size(500, 500);
  background(0);
}

void draw() {
  stroke(255, transparency);
  
  for(int i=0; i < 30; i++) {
    
    // create two random numbers to use as the line's starting point
    float startX = random(randomOffset * -1, randomOffset);
    float startY = random(randomOffset * -1, randomOffset);
    
    // create two random numbers to use as the line's ending point
    float endX = random(randomOffset * -1, randomOffset);
    float endY = random(randomOffset * -1, randomOffset);

    line(250 + startX, 250 + startY, 250 + endX, 250 + endY);
  }
  
}