Mio Path / Guide
Best one-line puzzle game for iPhone and Android.
"One-line puzzle" covers two different games: connecting every dot with a single stroke, and filling every tile of a grid with one path. Both scratch the same itch. This is how four apps compare, our own included. The facts come from the store listings of September 2026.
What to look for
The rule: dots and edges (draw every line once) or tiles (visit every square once). Tile puzzles allow extra mechanics such as arrows, ice and portals; dot puzzles stay closer to a pencil riddle.
Levels: handmade levels carry one idea each; generated levels give volume. Both are fine, but they feel different after a hundred puzzles.
Pace: a timer or a lives system pushes you; a relaxed game lets you look at a board for as long as it takes.
Money: free apps live on ads and hints. Check what a single purchase removes.
Mio Path (OLYMPHEON)
Our own app, so read this as the maker's description. A tile puzzle: draw one continuous path that touches every tile exactly once. New rules arrive one at a time across themed packs: arrows, ice, colours with shape backups for colour-blind play, keys, portals and switches. More than 2,500 handmade levels, no timers, fully playable offline, 34 languages. Free with ads; one purchase removes them. For iPhone, iPad and Android.
Fill (GAMINCAT)
The closest match in rule: fill every square of the board with a single line. About 2,000 puzzles in four difficulty levels, with hints for the hard ones. Free to download. Pick it if you want the pure tile rule without extra mechanics.
1LINE (GAMINCAT)
The dot version: connect all the points with one stroke without lifting your finger, in 850 stages across 15 levels, with one-way and overlapping lines later on. Free with ads; a purchase removes them, and hints are sold separately. The classic pencil riddle as an app.
Flow Free (Big Duck Games)
Not strictly a one-line puzzle, but the one people often mean: connect matching colours with pipes until every cell of the grid is filled. More than 2,500 free levels, daily puzzles and an optional time trial. It has been around since 2012, and the polish shows.
Where to start
If you want the tile rule with rules that keep changing, start with Mio Path: free on the App Store and Google Play, and the first packs show the whole idea. If you want dots and a pencil feel, 1LINE. Not sure what a one-line puzzle is? Read the short explainer first.