Recursive tree structure with angles depending on mouse position

tree.pde

//Autor: Christopher Schölzel

float angle = 0;

void setup() {
  size(400,400);
}

void draw() {
  background(255);
  translate(width/2.0,height);
  drawTree(angle,0.7,100);
}

void drawTree(float rotation, float ratio, float len) {
  if (len < 5) return;
  println(len);
  line(0,0,0,-len); //linie mit länge len gerade nach oben zeichnen
  pushMatrix();
  translate(0,-len);
  rotate(rotation);
  //rechte Verzweigung
  drawTree(rotation,ratio,len*ratio);
  popMatrix();
  pushMatrix();
  translate(0,-len);
  rotate(-rotation);
  //linke Verzweigung
  drawTree(rotation,ratio,len*ratio);
  popMatrix();
}

void mouseMoved() {
  angle = map(mouseX,0,width,0,HALF_PI);
}