c# objects fields: CS0246 CS0841

I've followed the video twice now and bother times I get the following

Game.cs(7,13): error CS0246: The type or namespace name Map' could not be found. Are you missingTre ehouseDefence' using directive?
Game.cs(9,13): error CS0841: A local variable map' cannot be used before it is declared Game.cs(10,13): error CS0841: A local variablemap' cannot be used before it is declared
Game.cs(12,22): error CS0841: A local variable `map' cannot be used before it is declared
Compilation failed: 4 error(s), 0 warnings

I've written the code exactly the same as in the video.

Here's my code

(Game.cs)

namespace TreehouseDefense
{
    class Game
    {
        public static void Main()
        {
            Map map = new Map();

            map.Width = 8;
            map.Height = 5;

          int area = map.Width * map.Height;
        }
    }
}

(Map.cs)

namespace TreehouseDefence
{
  class Map

  {
    public int Width;
    public int Height;
  }

}

Any help would be appreciated.