How to read the board
Tap an edge to cycle: empty → line → not-a-line (×) → empty.
Solid line = part of the loop. Faint × = marked as definitely not a line. Dashed blue = a forced move you haven't drawn yet (Show forced moves / Reveal one).
Red ring/glow = a mistake — a clue or loop rule that's already broken.
Green ring = solved, every clue satisfied.