diff --git a/classes.cpp b/classes.cpp
index 825b257..2e884fc 100644
--- a/classes.cpp
+++ b/classes.cpp
@@ -5,34 +5,80 @@ class Animal {
   public:
     // Note: using *virtual* does the difference here!
     virtual void makeSound() {
-      std::cout << "<generic animal sound>" << std::endl;
+      std::cout << "<generic animal sound> from " << this << std::endl;
+    }
+
+    Animal& operator= (Animal &a) {
+      std::cout << "lol, operator= of " << this;
+      std::cout << "(arg: " << &a << ")" << std::endl;
+
+      return *this;
     }
 };
 
 class Cow : public Animal {
   public:
     void makeSound() {
-      std::cout << "Mooh." << std::endl;
+      std::cout << "Mooh. from " << this << std::endl;
     }
 };
 
 class Cat : public Animal {
   public:
     void makeSound() {
-      std::cout << "Meow?" << std::endl;
+      std::cout << "Meow? from " << this << std::endl;
     }
 };
 
+void call(Animal a) {
+  a.makeSound();
+}
+
+void callref(Animal &a) {
+  a.makeSound();
+}
+
+void callptr(Animal* a) {
+  a->makeSound();
+}
+
 int main() {
   Cat cat;
   Cow cow;
 
+  std::cout << "== Some animals" << std::endl;
+  Animal animal;
+  animal.makeSound();
+  call(animal);
+  callref(animal);
+  callptr(&animal);
+
+  animal = cat; // <- lol, operator
+  animal.makeSound();
+  call(cat);
+  callref(cat); // <- meow
+  callptr(&cat); // <- meow
+
+  animal = cow; // <- lol, operator
+  animal.makeSound();
+  call(cow);
+  callref(cow); // <- mooh
+  callptr(&cow); // <- mooh
+
+  std::cout << "== refs" << std::endl;
+  Animal &aref = cat;
+  aref.makeSound(); // <- meow
+  aref = cow; // <- lol, operator
+  aref.makeSound(); // <- meow, still
+
+  std::cout << "== vector<Animal>:" << std::endl;
   // Does nothing:
-  std::vector<Animal> animals = { cat, cow };
+  std::vector<Animal> animals = { cat, cow }; // <- Copies
   for (auto &a: animals) {
     a.makeSound();
   }
 
+  std::cout << "== vector<Animal*>:" << std::endl;
   // Meow? Mooh.
   std::vector<Animal*> animalptrs = { &cat, &cow };
   for (auto &a: animalptrs) {