Fighting for score

We've got a lot in place; now we just need to put these parts together in another way to add in some more gameplay, in the form of bullets that will be fired at the enemy.

Let's begin by creating a Bullet class; this will allow us to control the movement of the bullet and easily manage lifetime and damage.

class Bullet
{
private:
  RectangleCollider *_collider;
  std::shared_ptr<Sprite> _sprite;
  bool _isAlive;

public:
  int Damage;

  Bullet();
  ~Bullet();

  void Load();

  RectangleCollider* GetCollider() { return _collider; }

  void SetPosition(XMFLOAT2 topleft);
  void MoveForward(float deltaTime);

  void Destroy();
  void Respawn();
  bool GetIsAlive();
};

There's quite a bit in here, but most of it you have seen before. We need a Sprite and a collider for the bullet so that we can display it and easily check for collisions with the enemy. We use SetPosition to set the initial position when we spawn the bullet, and MoveForward to let the bullet...