Masyu (Pearls)

Masyu (published in English as Pearls) is a loop puzzle: you draw one single closed loop through the centres of cells, moving only horizontally and vertically, and the loop must pass through every white and black pearl without ever crossing or touching itself. There are no numbers anywhere; the only clues are the white and black pearls (small circles) printed in some of the cells, and the loop must pass through every one of them.

What does a white pearl do?

The two kinds of pearl pull the loop in opposite ways, and learning their rules precisely is the whole game. At a white pearl the loop must go straight through the cell — entering one side and leaving the opposite side, never turning on the pearl itself. But it cannot run straight forever: the loop must turn in at least one of the two cells immediately before or after the white pearl. In other words, a white pearl sits on a straight segment that bends within one step on at least one side, so it can never lie on a long, perfectly straight run with no corner near it.

What does a black pearl do?

At a black pearl the rule is the mirror image. The loop must turn at the pearl, making a 90-degree corner in that cell rather than passing straight through. And it must go straight through both cells immediately before and after the turn — so on each side of a black pearl the loop travels at least one full cell in a straight line before it is free to bend again. A black pearl therefore always sits at the elbow of an L that has a straight arm of length at least one on either side.

Does every Masyu have one solution?

Because every pearl is a hard constraint and the loop must be a single closed ring, a well-made Masyu has exactly one solution reachable by pure logic. There is never any need to guess: each pearl, and each cell the loop has already entered, forces the next segment somewhere on the board. Every puzzle on this page is generated and checked to guarantee that unique answer.

The core Masyu strategy is to squeeze the pearl rules against the edges of the grid and against each other, working the most constrained pearls first. These are the core masyu tips, and they cover almost every opening move you will need:

What are the key Masyu deduction patterns?

• A black pearl near an edge has its turn fixed. A black pearl needs a straight cell on both sides, so it can never sit one cell away from a wall in the blocked direction. If a black pearl is in the second row from the top, it cannot run upward (there is no room for a straight cell above), so it must run downward — and the same logic fixes its left-or-right arm. Often this pins both arms and settles four segments at once.
• Two white pearls in a straight line force the loop straight through both. Each white pearl must be straight, so if two of them are lined up in the same row or column with nothing forcing a bend between them, the loop runs straight along that whole stretch, passing straight through both pearls.
• A black pearl next to another pearl is heavily constrained. Because a black pearl shoots a straight segment out of both sides, a pearl sitting right beside it must accept that straight segment passing through or up to it — frequently forcing the neighbour’s direction too. Two black pearls adjacent in a line is impossible, so that arrangement immediately tells you which way each one turns.
• A white pearl on or near an edge often runs along the edge. A white pearl in the outermost row or column must go straight, and along a wall the only straight line is the one parallel to that wall — so the loop runs straight along the edge through the pearl, then must turn just beside it to stay on the board.
• Watch for dead ends. Every cell the loop enters needs both an entrance and an exit. If a segment would reach a cell that has no legal way out — boxed in by walls or by the no-crossing rule — that segment is wrong, so cross it off as forbidden.

Where should you start solving?

The reliable habit is to work the pearls near the border first, where the loop has the fewest choices, then let each forced segment constrain the cells beside it. Mark the gaps you have ruled out as well as the segments you have drawn — a forbidden segment is just as much information as a drawn one. And never guess: on a proper Masyu there is always a pearl or a half-finished cell that forces the next move.

A white pearl means the loop passes straight through but must bend in an adjacent cell; a black pearl means the loop turns 90° on the pearl but runs straight through the cell on each side. The whole character of Masyu lives in this contrast between its two pearls, so it is worth holding them side by side:

A white pearl says “pass straight through me, but bend nearby.” The loop must run straight across the pearl’s own cell, yet it must turn within one cell on at least one side. The practical consequence: a white pearl can never lie in the middle of a long straight corridor with corners far away — there has to be an elbow right next door. White pearls in a row, by contrast, happily share one straight run.

A black pearl says the opposite: “turn on me, but go straight on both sides.” The loop must make its corner in the black pearl’s cell, and it must travel at least one full straight cell out of each arm before bending again. The practical consequence: a black pearl needs breathing room. It cannot sit one cell from a wall in the direction it would need to run straight, and it can never be directly adjacent to another black pearl in a straight line, because their straight arms would collide. Keep these two opposite demands clear — straight-here-bend-beside for white, bend-here-straight-beside for black — and most of the board’s logic falls out naturally.

A black pearl tucked just inside a corner is forced to turn down-and-right, and two white pearls sharing a row force the loop straight through both — a few opening moves that show how the pearl rules chain into a solution.

How do you open from a corner black pearl?

Picture a black pearl sitting in the cell just inside a corner — second row, second column. A black pearl must run straight for a full cell on both of its arms, but pointing up would need a straight cell above it and there is only the wall, and pointing left would need a straight cell to its left and again there is only the wall. So this black pearl is forced to turn with one arm heading down and the other heading right, each running straight for at least one cell into the board. With one pearl, you have placed four certain segments.

How do the segments chain together?

Now suppose two white pearls sit in the same row with one empty cell between them. Each must be straight, and there is nothing to make the loop bend in that short stretch, so the loop runs straight along the row through the first pearl, across the gap, and straight through the second. That settled run then meets the segments you drew from the black pearl, and where they join, the no-crossing rule and the “every cell needs an exit” rule force the next turn. Take each forced segment, re-scan the neighbouring cells, and the single loop assembles itself — no guessing at any point.

This page offers Masyu at two sizes — 5×5 and 6×6 — with the same rules; the 5×5 is the gentle starter and the 6×6 gives the loop more room to wander, so its deduction chains run longer.

How hard is 5×5 versus 6×6 Masyu?

The 5×5 board is the gentler one — a short, tidy loop with pearls close to the walls, which makes the forced moves easy to spot and the whole solve a pleasant few minutes. It is the best place to get the white-and-black rules into your fingers. The 6×6 grid gives the loop far more room to wander, so the deduction chains run longer and there are fewer instant openings near the edges. The rules are identical; you simply hold more of the board in mind at once, and the interactions between distant pearls matter more. Difficulty in Masyu is less about raw size than about how the pearls are placed — pearls tucked against the border hand you free moves, while pearls floating in open space ask you to look several steps ahead.

How do New, Daily and Reset work?

Tap New for a fresh, uniquely solvable board at either size whenever you like, or play the shared Daily to take on the same loop as everyone else that day. If a board gets tangled, Reset clears your segments back to the bare pearls so you can think it through again from the start.

Masyu is the name used almost everywhere now, but in English it has long been published simply as Pearls, and sometimes as White Pearls and Black Pearls after its two kinds of clue — all the same puzzle with the same rules. Any tip you pick up under one name carries straight across to the others.

Masyu belongs to the family of loop puzzles, where the goal is to draw a single closed path under different rules. If you enjoy threading one continuous loop, try Slitherlink, where the loop runs along the grid lines and numbered clues tell you how many edges each cell uses. And for a related challenge in building one connected structure, Hashi has you wire numbered islands together with bridges into a single network. All three reward the same instinct — making one rule-obedient path or network — approached from a different angle.

A handful of words turn up in every Masyu guide — loop, segment, white pearl, black pearl, straight and turn — and here is exactly what each one means.

• Loop — the single closed ring you are building, threaded through the cell centres. It never crosses or touches itself, and it must pass through every pearl.
• Segment — one short piece of the loop joining two neighbouring cells, drawn by tapping the gap between them. The loop is just a chain of segments.
• White pearl — a hollow circle the loop must pass straight through, while turning in at least one of the two cells right beside it.
• Black pearl — a filled circle the loop must turn on, going straight through both cells immediately before and after.
• Straight — the loop enters one side of a cell and leaves the opposite side, with no bend in that cell. Required at every white pearl.
• Turn — the loop makes a 90-degree corner inside a cell, entering one side and leaving an adjacent one. Required at every black pearl.

The most common Masyu mistakes are letting a white pearl run dead straight with no nearby bend, turning straight through a black pearl, crossing or branching the loop, closing a small loop early, and guessing instead of scanning.

• Letting a white pearl run dead straight. It is easy to draw the straight segment through a white pearl and forget the second half of the rule — the loop must turn within one cell on at least one side. A white pearl on a long straight run with no nearby corner is illegal.
• Turning straight through a black pearl. The mirror slip: a black pearl must make a corner, not pass straight, and it needs a full straight cell on both arms. Cramming a black pearl against a wall with no room to run straight breaks the rule.
• Crossing or branching the loop. The path is one simple ring — no cell may have the loop passing through it twice, and no point may sprout three segments. Each cell the loop uses has exactly one way in and one way out.
• Closing a small loop early. Joining segments into a little ring while pearls elsewhere are still unvisited means starting over. The finished loop must be a single ring that passes through every pearl.
• Guessing instead of scanning. An unjustified segment can run a long way before it contradicts a pearl. There is always a forced move — re-check the pearls near the walls first.

Masyu is a beautifully pure logic workout: no arithmetic at all, just two pearl rules and one loop, yet from them grows genuinely deep spatial reasoning. You are constantly visualising how a segment here forces a turn there, tracing the path forward and backward, and weighing whether a move would strand a cell or break the single-ring rule. It sharpens pattern recognition, planning and patience in a calm, low-pressure way, and the moment the loop finally clicks shut is quietly satisfying.

It is also fair by design. With exactly one logical solution on every board, progress always feels earned rather than lucky — there is no dead end you could not have foreseen. A 5×5 makes a perfect short break; a 6×6 is a more absorbing sit-down solve. And if you like the way Masyu turns a few pearls into one exact loop, the same pleasure is waiting in Slitherlink and in the island-connecting logic of Hashi.

Masyu is a Japanese pencil puzzle from the publisher Nikoli — the house behind Sudoku and Slitherlink — that first appeared around 2000 and quickly became one of its signature loop puzzles. It spread from puzzle magazines into books and apps thanks to a design that needs nothing but a grid of pearls and clear thinking.

The name has a charming twist. The puzzle was originally called Shinju, written with characters meaning “pearls” — which is why it still appears in English simply as Pearls, or as White Pearls and Black Pearls. The current name, Masyu, is a playful re-reading of those same characters that instead suggests “evil influence” — a wry nickname for a puzzle whose innocent-looking circles can tie your loop in knots. Whatever you call it, the elegant core has never changed: white pearls and black pearls, one closed loop, and an answer reachable by pure logic.