Castle Wall (Masyu) by Mark Sweep
or solve online (using our beta test of Penpa-Edit tools in linex mode where left click+drag draws lines and right click marks X’s)
Theme: Slanted Squares
Author/Opus: This is the 2nd puzzle from guest contributor Mark Sweep.
Rules: Standard Castle Wall rules, but none of the clue colors are given. The solver should determine whether each gray clue is white or black. Also, the loop must go straight through the cells with white circles, with a turn in at least one of the cells immediately before/after each white circle. The loop must make a turn in all the black circles, but must go straight in both cells immediately before/after each black circle.
Difficulty: 3.5 stars
Time Standards (highlight to view): Grandmaster = 5:15, Master = 8:00, Expert = 16:00
Solution: PDF; a solution video is also available here.
Note: Follow this link for more Castle Wall puzzles. If you are new to this puzzle type, here are our easiest Castle Wall puzzles to get started on. More Castle Wall puzzles can be found in our beginner-friendly collection Intro to GMPuzzles as well as the larger collection Castle Wall, both by Serkan Yürekli.
Part logic … part trial and error …