Kuroshiro
Kuroshiro is a loop-drawing puzzle introduced by Nikoli (the exact year of origin is unknown). The puzzle features black and white circles placed on a grid; each circle restricts how many turns the loop may make between that circle and the next one it encounters. Although the rules are simple, the interplay between color-based turn limits and global loop structure creates rich logical deductions and a distinctive solving style.
Rules
Draw a single continuous loop in the grid using horizontal and vertical line segments so that the loop visits every cells with circles, other cells may remain unvisited. It should not cross or overlap itself. Between two consecutively visited circles of the same color, the loop must not turn. Between two consecutively visited circles of different colors, the loop must turn exactly once.
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