sclass AnimatedLine {
  int w = 128, h = 128, maxSpeed = 1;
  int y, speed;
  Graphics2D g;
  
  void setSize(int w, int h) {
    this.w = w;
    this.h = h;
  }
  
  void setGraphics(Graphics2D g) {
    this.g = g;
  }
  
  void start {
    y = random(h);
    newSpeed();
  }
  
  void newSpeed {
    speed = random(-maxSpeed, maxSpeed);
  }
  
  void paint {
    fillRect(g, 0, 0, w, h, Color.white);
    drawLine(g, 0, y, w, y, Color.black);
  }
  
  void nextFrame {
    if (oneIn(20)) newSpeed();
    y = clamp(y+speed, 0, h-1);
  }
}