Pearls

Draw one continuous loop that passes through the centre of cells, never crossing or branching, and threads every pearl. White pearls and black pearls each impose a shape on the loop where they sit, and you must satisfy all of them at once.

• The loop is a single closed line with no crossings or dead ends
• White pearl: the loop goes straight through it, but turns in at least one of the cells just beside it
• Black pearl: the loop turns at the pearl, and goes straight in the cells immediately beyond on both sides
• A pearl flashes red when its current surroundings already break its rule

• Desktop: left-click the segment between two cells to add or remove a loop edge; right-click marks a segment as empty with an x
• Phone & tablet: tap between two cells to draw or erase a loop segment

• Three sizes: 6x6, 8x8, and 10x10
• Daily puzzle shared by everyone that day, or unlimited Practice puzzles
• Clear wipes the board back to empty

• Pin down the black pearls first, they force a turn plus two straight segments, which often locks several edges at once
• Mark segments you know are empty to keep the path from branching by accident
• Watch the loop's edges and corners: each cell on the loop has exactly two connections

This puzzle's name is a mistake that stuck. It began in Puzzle Communication Nikoli #84 as Shinju no Kubikazari, 真珠の首飾り — "pearl necklace" — and in that first form it had only white circles.

Black circles arrived in #90, which deepened it considerably, and the puzzle was renamed Shiroshinju Kuroshinju, "white pearls and black pearls". Then the name Masyu appeared: a misreading of the kanji 真珠 by Nikoli's president, which became an office joke and was adopted as the official title in #103.

The rules stayed elegant through all of it. A single loop passes through every circle; it must turn on a black pearl and run straight through a white one, with the opposite condition applying to the cells immediately before and after. Two constraints, and the whole grid follows.

Pearls is a single-loop logic puzzle where black and white markers dictate where the line turns and where it runs straight. This is an original, free browser version with daily and practice puzzles at three sizes, no download or sign-up required.

A free, original browser game on PlayPendium. No download, no install.