Stained Glass

Stained Glass is a Nikoli puzzle in which the aim of the game is to color various fields a color based on the colors of the circles intersecting the edges of these fields.
Stained Glass can be played on any sized field, the difficulty won't change with it though as it comes from the amount of circles and lines dividing the main field into smaller fields.

The rules are as follows:
- All the smaller fields must be colored correctly according to the small circles.
- White circles indicate more than half the fields touching that circle must be white.
- Grey circles indicate half the fields touching it have to be black and half have to be white.
- Black circles indicate more than half the fields touching that circle must be black.

Standard version

Stained Glass is definitely a deduction game, but they're generally not that difficult to overcome. There are a few places you can often start to make an easy start, like finding white or black circles with only 2 fields. Both those fields will have to match the circle's color as dictated by the rules.

Another easy deduction is once you've figured out half of the fields around a grey circle are either black or white you know the others are the opposite color.
Similar deductions can be made for most sections of a puzzle, but they do depend on the neighboring circles to figure out.

Converting it to an RPG setting.

Converting Stained Glass to an RPG setting is trickier compared to most puzzles, but not impossible of course. The shaded shapes could mark water, then the white shapes could be land. It could be used to divide land between farmers or land owners, it could be used to show what land needs to be avoided, or where an attack might take place.
Another option is to hide an image in the shapes. It could be an angular looking animal, a letter, a rune or a crude looking symbol. Perfect for secret societies, spies, and covert operations for example.

In my example my character is faced with a seemingly ordinary land, which has been divided into farm fields. Seems innocent enough to her, but she did manage to retrieve the clue of the green circles, as well as the instructions on how to solve a Stained Glass puzzle.

If she manages to figure out the puzzle she'll figure out some of the fields have been marked by the puzzle's result and she'll be able to safely figure out what is tainting these farm plots. If she doesn't figure out the puzzle and decides to simply figure out the mystery of the fields on her own she'll likely tread on this cursed land and fall sick soon after stepping onto it.

If you're creating a custom Stained Glass puzzle make sure you add enough colored circles as hints, otherwise you end up with a puzzle that's either impossible to finish without making a guess or with a puzzle that has multiple solutions.
It's easy to create one though, simply divide a field into smaller fields, color some of them, and then add all the circles accordingly. Remove some if you added too many, turn the colored fields back into uncolored fields, and you're done.