Yin-Yang (also called Shiromaru-Kuromaru) is a Nikoli-style logic puzzle on a grid. Every cell must be filled with either a white circle or a black circle. Some cells start pre-filled as clues — these are fixed and cannot be changed.
Click an empty cell to cycle its value: empty → white → black → empty. Right-click (or long-press on mobile) jumps straight to black. The puzzle is solved when all four rules hold at once: the board is full, every white circle connects into one orthogonal group, every black circle connects into one orthogonal group, and no 2×2 block is a single colour.
Use the on-screen Hint button (or press H) to reveal one correct cell, Check (C) to validate your current board, Clear to wipe non-clue cells, and Restart (R) to reset the level. Press Esc to return to the menu. You earn up to 3 stars per level — solve without any hints for the perfect rating.
Watch the 2×2 rule first. The fastest deduction in Yin-Yang is the forbidden-monochrome block: whenever three cells of a 2×2 are the same colour, the fourth must be the opposite. The engine highlights any violated 2×2 in red, so scan for those red flashes before chasing connectivity.
Think in regions, not cells. Because both colours must each form a single connected group, a colour can never split into two disconnected islands. If filling a cell would isolate part of a colour from the rest, that placement is illegal — even if no 2×2 rule is broken. Use this to prune impossible branches early.
Work the borders and corners. Edge and corner cells have fewer neighbours, which forces stronger constraints. A corner circle, for example, can only extend its colour inward along two edges — filling the adjacent edge cells often cascades deductions across the whole board.
Toggle Auto-Check for a guided solve. The settings panel has an Auto-Check toggle that continuously validates your board and warns about 2×2 violations and disconnections as you play. Turn it on while learning, then switch it off for a purist challenge and a clean 3-star run.
Yes — Yin-Yang is 100% free, with no download, no sign-up, and no ads inside the puzzle itself. Just open the page and start solving.
Absolutely. The board resizes to fit any screen, and taps work exactly like mouse clicks — tap to cycle white → black → empty, long-press to place black directly.
30 hand-verified levels across five difficulty tiers: Beginner (5×5), Easy (6×6), Medium (7×7), Hard (8×8) and Expert (9×9). Every level has a single unique solution confirmed by an independent solver.
Yes. Solved levels, star ratings, and the level you're currently on are saved automatically in your browser (localStorage). Close the tab and come back any time — you'll resume right where you left off, on any device.
Circles with an inner ring are clues — pre-filled cells that are part of the puzzle and cannot be changed. Plain circles are ones you placed yourself.