Nice, glad you enjoyed it! I've been thinking about ways I could have clued the secrets better - this was a good learning experience to help me fine tune how much guidance would be the right amount. I have a few ideas for how I could give just a little tiny extra nudge here and there.
Yeah it's a tough balance. If the secrets were more obvious, it wouldn't have been as rewarding to find them, so for me it seemed about right as-is. Of course that exact balance varies from person to person. In this case, I might not have known that the "????" represented extra levels, except for the fact that I was expecting 16 levels and the list stopped after 13.