Masyu: Line Logic

Masyu is a classic puzzle also known as Pearl. Draw one loop through the centers of the cells, with no crossings or branches. The loop passes through every circle, but it doesn't have to visit every cell.
On a white circle the loop goes straight, and it turns in the cell just before or just after it, or both. On a black circle the loop turns, and on both sides it goes straight through the next cell.
Every puzzle has exactly one solution, and you can always work out the next step with logic, so you never have to guess.
If you like Sudoku, it's a similar kind of logic puzzle, no luck needed.

Features:
A new daily puzzle, the same for everyone, that builds up in difficulty through the week

A calendar for catching up on dailies you missed

15,000 puzzles in Endless mode, on 6×6, 8×8, 10×10 and 12×12 boards

Four difficulty levels, Easy to Expert, based on the techniques a puzzle needs, not just its size

Saved progress and best times, and a stats page with your totals

Solving Help:
A tutorial that teaches the rules and all 26 techniques, Easy to Expert

Hints that show the next step a little at a time, and a check for mistakes

A different color for each separate piece of line, so you can see what still needs joining

Leftover sides crossed out for you when two lines meet in a cell, and finished circles faded (both optional)

Rule breaks shown right away, like a branch, a circle that can't keep its rule, or a loop that closes too early

Settings and Controls:
Optional shading inside or outside the loop

Undo and redo, even after clearing the board

A timer you can hide, and a pause screen that hides the board

Light and dark modes, three color themes, an option for bolder lines and circles, and soft sounds

Mouse or keyboard controls