I find that whether these puzzles are easy or hard must be highly subjective. Some of the easier I have a heck of a time figuring out what M's train of thought is, some of these harder ones, I can see it almost immediately. I must say, I am still trying to figure out exactly how the purple symbol works. It seems to fit the binary thing, at times, but its function doesn't seem to be as simple as the other symbols. I'll keep working on that. But I didn't need it work out the answer in a trice. I _like_ this kind of puzzle!
And, like ReverendTed, I appreciate when I don't have to resort to a hint. It's so much more satisfying.