Ok, i have tried many lighting system and yours is the best i have seen. I can easily do what i want with your demo but i failed to implement it in my game.
In your demo, the drawing is made in a principal class -> called by the game class.
But my light need to be drawn in a:
background class -> drawn in the gameplayscreen class -> inheriting from a screen display class -> with a graphics device coming from a screen management class -> called by main game class.
This create a lot of problem to load, initialize or Draw. For example:
-(This) is often used but not necessarily point to the good class, inheritance should be different too, i think
-in my Background Draw class, the call is Draw(SpriteBatch spritebatch) which make the gameTime inaccessible for your engine.
A tutorial would be the best thing you'll can do for the use of your engine. Anyway, good job on what you did with Krypton.