Added some structuring.

The game runs but only a black window is shown.

src/placeable.hpp

@@ -7,6 +7,7 @@ namespace cloonel {
 	class Placeable {
 	public:
 		const float2& GetPos ( void ) const noexcept { return m_pos; }
+		void AddOffset ( const float2& parOffset ) noexcept { m_pos += parOffset; }
 
 	protected:
 		Placeable ( float parX, float parY );