float angle= 0.0;

void setup(){
  size(400,400);
  smooth();
  background(255); //set background to white
}

void draw(){
  translate(mouseX, mouseY); //square follows mouse
  rotate(angle); //square will rotate
  strokeWeight(2); //stroke is thickness of 2
  rect(-15,-15,30,30); //square
  line(0,0,400,400); //lines coming out of square
  angle += 0.2; //degree of angle rotation
}

void mousePressed(){
  fill(60,20,250); //when pressed square is red
  if(mouseX<200){ //if mouse is pressed <200
    fill(255,0,0); //square turns blue
  }
}