Astonishing lvl El!!! 5/5 for sure and excellent skill to Monty as well for being the first to solve it. Congratulations and may I add that we have missed ur unique creations El.
Yes it is. That was very hard. I think perhaps it would be better if you made it a 3x3 version. It would give it a higher white to colour ratio making it easier. How do you come up with such great ideas?