int d = 5; //diameter
int n = 5; //recursions

void setup() {
  size(300,300);
  background(0);
  noFill();
  stroke(255);
  smooth();
}

void draw() {
  background(0);
  Curve (mouseX, mouseY, d, n);
}

void Curve (float x, float y, float d, int num) {
  bezier(-100, 0, x, y, x-n*d, y-n*d, 500, 0);
  if (num > 1) {
    num = num - 1;
    int branches = 3;
    for (int i = 0; i < branches; i++) {
    float a = random(0, 3);
    float newx = x + a * num;
    float newy = y + a * num;
    Curve (newx, newy, d*1.5, num);
    }
  }
}