Amazing puzzlebook!
I don't understand how 3-C, 5-4, and Fin have unique solutions, though. (The two solutions I have for 5-4 have the same answer code, and I may be completely misinterpreting the Finale.)
I see the Spoiler button between Strikethrough and Lists. Must be new.
I may be more off-track than I thought. For 5-4 I was thinking the solution could be
- All orange, because there's no I tetromino in this shape.
- All white, because... there's no need for any other color, and there's no T-tetromino-shaped island. 1-C doesn't require any player shading, but I guess the implicit rule could be that it can't just be all white.
The book's answer code for 3-C doesn't make sense to me at all.
POTENTIAL SPOILER IMAGE BELOW
(Testing spoiler feature on image)
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Apparently the cell I've marked with a question mark needs to be green? Even though that would divide the white region? Also the bottom row allows for multiple solutions. Again, I may be way off-track at this point.
Sorry, I think my comment was confusing, you're absolutely on the right track! To get an idea of how close you are: For 5-4, one of your two answers is right. 1-C's uniqueness doesn't rely on "shade some cells", though that's indeed a rule. 3-C indeed needs green on that ?. All of these are based on just the 3 big rules. edit: I think you've pretty much understood the implicit rules?