E.g. I am on level 19. I solved everything else on the level except one spot. I can tell that the bottom right spot is blue , but I don't have enough information to determine if it should be a house or a tower. Or am I missing a rule somewhere? Or if something CAN be a tower, it MUST be a tower? (the rules don't make this explicit, and I think I've seen counter-examples? But maybe I'm mistaken)...

I marked the two obvious reds and one obvious blue, and... now what? I can come up with a layout where any tile is blue or red, or has at least 2 of the three buildings as valid options.

I'm completely stuck here. I can identify 3 reds and 1 blue which are "obvious", and beyond that there seem to be way too many possible permutations to be able to say anything at all. Am I just stupid?