Midpoint perpendicular points (Processing 3)

// midpoint perpendicular points
// drag mouse left or right to move points
// move wheel to adjust the distance

// Code for Processing 3

float x1 = 0, y1 = 0;
float x2 = 0, y2 = 0;

float newLen = 30;

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

void draw(){
  background(255);

  line(x1, y1, x2, y2);
  circle(x1, y1, 12);
  circle(x2, y2, 12);

  float cx = (x1+x2)/2;
  float cy = (y1+y2)/2;

  float dx = x1 - cx;
  float dy = y1 - cy;
  float len = sqrt(dx*dx + dy*dy);

  float fx1 = dy/len*newLen + cx;
  float fy1 = -dx/len*newLen + cy;
  circle(fx1, fy1, 20);

  float fx2 = -dy/len*newLen + cx;
  float fy2 = dx/len*newLen + cy;
  circle(fx2, fy2, 20);

  line(fx1, fy1, fx2, fy2);
}

void mouseDragged() {
  if (mouseButton == LEFT) {
    x1 = mouseX;
    y1 = mouseY;
  } else if (mouseButton == RIGHT) {
    x2 = mouseX;
    y2 = mouseY;
  }
}

void mouseWheel(MouseEvent event) {
  newLen += event.getCount()*5;
}