Masyu

Nikoli introduced Masyu in Puzzle Communication issue 84 in 2000, originally calling it Shinju no Renzoku, or Pearl Sequence. The puzzle asks you to draw a single closed loop through a grid of black and white pearls, with each pearl color imposing its own turning rule. Solving Masyu trains spatial reasoning and constraint propagation, the same skill that powers logic programming. Black pearls force corners, white pearls demand straight passages, and the loop must never cross itself. Trace your first loop and solve the grid.

1. Open the Masyu grid and locate every black and white pearl. The goal is to draw one continuous loop that passes through all of them.
2. Click an edge between two cells to draw a line segment. Click again to remove it if you make a mistake.
3. At a white pearl, the loop must pass straight through that cell and turn in at least one of the adjacent cells on either side.
4. At a black pearl, the loop must make a 90-degree turn inside that cell, then continue straight through the next cell in both directions.
5. Extend segments from forced pearls outward. Black pearls near a border often have only one legal turning direction, which locks the first segments.
6. Connect every segment into a single closed loop with no branches, no crossings, and no loose ends to finish the puzzle.

• The solution is exactly one closed loop. It has no branches and no self-crossings.
• The loop must pass through every pearl on the grid.
• At a white pearl, the loop travels straight through the cell and turns in at least one neighboring cell immediately before or after.
• At a black pearl, the loop turns 90 degrees inside that cell and extends straight through the adjacent cell in both directions.
• The loop only travels horizontally or vertically between side-adjacent cells. Diagonal movement is not allowed.
• Cells without pearls can still be part of the loop as long as all pearl rules are satisfied.

• A black pearl on the edge or in a corner has only one legal turn direction. Draw that turn immediately to anchor the opening.
• A white pearl with both neighbors already straight cannot have the loop pass straight through it, because it needs a turn nearby. Mark that cell as unused.
• Extend every forced segment at least two cells past a black pearl. The straight-through rule after a black turn often creates chains that cross the grid.
• Reject any segment that would close a small loop before all pearls are visited. The final answer is one loop, so premature closures are always wrong.
• Use border geometry to eliminate impossible edges. A pearl one cell from the border cannot send a straight segment off the grid, which restricts its options.
• Check for isolated regions. If drawing a segment would cut off a group of unvisited pearls, that segment is invalid.

• Slitherlink: Slitherlink also asks you to draw a single loop on a grid, but uses numbered vertices instead of colored pearls to control segment counts.
• Nurikabe: Nurikabe shares the grid-deduction DNA with Masyu but asks you to shade cells and form islands instead of drawing a loop.
• Masyu with gray pearls: Some variant puzzles add gray pearls that act as either black or white, determined by the solver. This increases the deduction difficulty significantly.

• Every confirmed segment ripples across the grid, creating satisfying chain reactions.
• The two pearl rules are simple to learn but generate deep logical paths.
• No numbers are involved, so the puzzle relies purely on geometry and spatial reasoning.
• Solving a grid produces a clean, elegant loop that feels like a completed drawing.
• Puzzles range from quick five-minute warm-ups to extended challenges that fill a commute.

Play Masyu online for free on Clasica Games. Click edges to draw line segments, watch the loop grow in real time, and remove segments with a second click if you need to backtrack. The interface highlights connected paths so you can spot loose ends instantly. No download or account needed. Open a puzzle and trace your first loop.

Masyu turns a grid of pearls into a geometric deduction challenge. Read the black and white clues, extend forced segments, and connect everything into one clean loop. Open a free puzzle and trace your first path.

• Nikoli Masyu rules
• Masyu overview