Olho

int bolaOlhoD = 100;
int fundoOlhoD = 250;

void setup(){
  size(800,800);
}

void draw(){
  background(125);
  fill(255);
  fundoOlho();
  fill(0);
  bolaOlho();
}

void fundoOlho(){
  strokeWeight(5);
  ellipse(width/2,height/2, fundoOlhoD, fundoOlhoD);
}

void bolaOlho(){

  int x = mouseX;
  int y = mouseY;

  int distancia = distancia2D(width/2, height/2, x,y);

  if(distancia > fundoOlhoD/2 - bolaOlhoD/2){
     float angulo = atan2(y-height/2,x-width/2);

     y =  height/2 + (int)(sin(angulo)*(fundoOlhoD/2 - bolaOlhoD/2));
     x = width/2 + (int)(cos(angulo)*(fundoOlhoD/2 - bolaOlhoD/2));
  }



  pushMatrix();
  ellipse(x, y, bolaOlhoD,bolaOlhoD);
  popMatrix();
}

int distancia1D(int A, int B){
  return abs(A-B);
}

int distancia2D(int A_X, int A_Y, int B_X, int B_Y){
  return round(sqrt( pow(distancia1D(A_X,B_X), 2) + pow(distancia1D(A_Y,B_Y), 2) ));
}