Solutions

Exercise 1

Incorporate the Option return type to signify that a user may or may not be found:

public Option<Tower> GetTowerByPosition(Vector2 position)
{
     var tower = _gameMap.FindTowerAt(position);
     return Option<Tower>.Some(tower);
}

Exercise 2

Utilize a built-in check for null inputs that will throw an exception if the user profile is null:

public void ApplyPowerUp(Tower? tower, PowerUp? powerUp)
{
     ArgumentNullException.ThrowIfNull(tower, nameof(tower));
     ArgumentNullException.ThrowIfNull(powerUp, nameof(powerUp));
     tower.ApplyPowerUp(powerUp);
     _gameState.UpdateTower(tower);
}

Exercise 3

Employ pattern matching to address potential null values elegantly:

public string DescribeEnemy(Enemy? enemy)
{
     return enemy switch
   ...