void setup() {
  size(512, 256);
  noLoop();
}

void draw() {
  background(255);
  stroke(64);
  noFill();
  for (int i = 0; i < width; i++) {
    float randomVal = random(1);
//    float randomVal = getRandomProb();
//    float randomVal = noise(i * 0.01);
    randomVal *= height;
    line(i, height, i, height - randomVal);
  }
}

float getRandomProb() {
  float r = random(100);
  if (r < 10) {
    return 0.1;
  }
  else if (r < 60) {
    return 0.6;
  }
  else {
    return 0.75;
  }
}

void mousePressed() {
  redraw();
}