float x1,y1,x2,y2;

void setup() {
  size(400,400);
  background(0,100,200);
  x1=width/2;
  y1=height/2;
  x2=width/2;
  y2=height/2;
  rectMode(CENTER_DIAMETER);
}

void loop() {
  background(0,100,200);
  noFill();
  stroke(0);
  rect(x1,y1, 20,20);
  stroke(255);
  rect(x2,y2, 20,20);
  
  line(x1,y1, x2,y2);  
  line(x1,y1, x2,y1);
}

void mousePressed() {
  x2=x1;
  y2=y1;
  x1=mouseX;
  y1=mouseY;
  println("distance "+distance(x1,y1,x2,y1)+
    " angle "+angle(x1,y1,x2,y2));
}

float distance(float px1,float py1,float px2,float py2) {
  float xD=px2-px1;
  float yD=py2-py1;
  return sqrt(xD*xD+yD*yD);
}

float angle(float px1,float py1, float px2,float py2) {
  float xD=px2-px1;
  float yD=py2-py1;
  return degrees(atan2(yD,xD));
}