The Doppit Almanac · No. 39

Pearlit

Thread one loop past every pearl

What it is

Pearlit is Masyu. The board is a grid of dots with pearls sitting on a few of them, and you draw one closed loop from dot to dot, up, down, left and right. It never branches, it never crosses itself, and it can leave dots out. The pearls say nothing about where the loop goes. They say what it has to do when it gets there.

A hollow pearl runs the loop straight through, and then the loop has to turn at one of the two dots beside it on that line. A solid pearl is the other way round: the loop turns on it, and runs straight through the next dot at both ends. Neither one tells you which direction, so the walls usually break the deadlock first. A pearl against an edge has one fewer way to be.

How it plays

Draw one closed loop through the dots. It runs up, down, left or right, and never branches or crosses itself.
The loop runs straight through a hollow pearl and turns at one of the two dots beside it on that line.
The loop turns on a solid pearl and runs straight through the next dot on both sides.
Every pearl is on the loop. Dots with no pearl can be left out of it.
Draw puts a line between two dots, Cross marks a line the loop skips. Tap a line, or drag along a run of them.
Crosses are only your notes; the win ignores them. Stuck? Hint names the next forced line.

The difficulties

Easy is eight by eight with a short loop, mostly reading pearls against the walls. Medium is ten by ten, where the loop is long enough that closing it too early is the mistake to watch for. Hard is twelve by twelve with only the pearls the solve still needs, so every board has stretches where you take one line, follow it until it breaks a rule, and only then know which way the loop went. Expert is the same twelve by twelve, kept for the boards where that is not enough: you take a line, follow it to a dot with two ways on, and have to rule out both of those before the first line is settled. Expert is practice only, and it is long. A fresh board is dealt every day, for nothing.

Play today's board