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Upside-down Y: negation symbol. Denotes one incorrect symbol in its region.
Triangles: denotes the number of adjacent edges to the square.
Blue shape: subtracts from yellow shapes.
Yellow shape: must be in a region shaped like the sum of all yellow shapes in its region.
Square: must not have a square of another color in its region.
Star: must have exactly 2 objects of that color in its region. The edge case is that a negation and white star alone in a region in The Witness will be marked correct, while in The Windmill it won't.
Dot: Must be drawn over.