Masyu techniques

Masyu looks sparse, but every pearl gives you something. Black pearls near the edges and white pearls in rows are where most puzzles start. Mark squares the loop can’t use as you go, so you can see where it’s forced.

In each picture, the cells the technique decides are outlined in blue.

1. Black pearls by the edge

   A black pearl turns and runs straight for two squares each way. Next to the edge there’s no room on that side, so the loop must leave in the opposite direction, straight for two squares.

2. White pearls on the edge run along it

   The loop goes straight through a white pearl. On the edge it can’t go straight across the edge, so it runs along it.

3. Three whites in a row

   If three white pearls sat on one straight run, the middle one couldn’t have a turn beside it. So the loop crosses each of them the other way.

4. Two blacks side by side

   A black pearl can’t run into its neighbour, because the loop would have to go straight through a black pearl. So each one heads away from the other, two squares straight.

When you’re stuck, follow a loose end: a line that can only continue one way must go that way. And watch for small loops. The finished loop is a single circuit through every pearl, so any line that would close a smaller loop is ruled out.