One Continuous Line, Zero Room for Backtracking
The rule in Lines to Fill sounds almost too simple to be a real puzzle: draw one unbroken path that covers every cell of a shape without ever crossing itself. But that single constraint quietly rules out most of the obvious approaches, since filling a shape efficiently usually means committing to a route early that will still have somewhere to go by the time you reach the far corners. Larger shapes make this dramatically harder, because a path that seems perfectly reasonable through the first half of the grid can trap you in a dead end with cells still unfilled and no legal move left to reach them.
Tracing the Path Without Crossing It
Click and drag, or tap and swipe on mobile, to draw your line cell by cell through the shape, extending the path in any open direction as long as it doesn't cross a segment you've already drawn. Study the shape's overall layout before committing to a starting direction, since certain starting points make it mathematically impossible to reach every cell without a self-intersection.
- Look for narrow sections or corners early, since those cells often need to be reached before the surrounding area fills in.
- Avoid boxing yourself into a dead end by leaving a path back out of tight corners until they're actually being filled.
- Trace a rough route mentally before drawing, rather than committing to the first open direction available.
- Restart immediately once you spot an unreachable cell rather than continuing a path that can't finish.
- Work through larger shapes in mental sections, treating each cluster of cells as its own smaller sub-puzzle.
If calm, spatial-reasoning puzzles are your thing, the beam-routing logic of Light the Lamp offers a similarly relaxing brain-training session. Discover more puzzle games on our all games page.
