EXTEN does have feedback and provides the necessary information for the player to deduce and solve the puzzle. How else would at least nine people be confirmed to have solved it?
The various combinations of lights in accordance with their block positions have been designed in such a way that the player can figure out how the system functions and in turn derive the solution.
If I were to post a puzzle you could not solve I would certainly be disgraced by the puzzle community as a whole, there is a method to the madness.
At the same time I do acknowledge that this is a very esoteric and uncommon genre, I certainly wish black box puzzles were more used since they make for a very fun solving process.
If you would like hints, I am certainly willing to oblige. This is my favorite creation (even more than HOUSE!) and I would love to help you beat it.
Kindest regards
-Razurazu