How to play
Lattice Five is Morpion Solitaire (Join Five) — a solitaire played on grid paper since the 1970s. The rules fit in a paragraph; mastering them doesn’t.
The move
Place one new dot, then draw a straight line through five dots in a row — horizontal, vertical, or either diagonal. The line has to run through the dot you just placed. Your score is the number of lines you draw.
The one rule that matters
Two lines running the same direction may share an end dot, but they can never overlap — no stretch between two dots is ever drawn twice. Every line you draw uses up four of those stretches for good, which is why a board slowly closes in on itself.
In the stricter 5D variant, even sharing that one dot is out: lines along the same direction may not touch at all.
Five in a row is not a line
A move has to add a dot, and the line has to pass through it. Five dots that were already sitting in a row are worth nothing — and if one placement opens up two lines at once, you draw one and lose the other.
Gaps you close off
When two of your lines end up a few dots apart along the same direction, nothing can ever span the space between them. The app marks those dead gaps faintly in red, as you play and in replays — a quiet note that some room went to waste.
How good is good?
On the classic cross under 5T rules, beginners typically reach the 40s–60s. The human record of 170 was set by hand in 1976 and stood for 34 years; the best computer-found game is 178. Nobody knows the true maximum — only that it’s at most 485.
In the app
- Tap an empty point to see every line it could make; tap a line to play it. Drag over the candidates and lift to choose. Hover works too, with a mouse or trackpad.
- Slide a finger across the board and it buzzes wherever a dot can go, so you can hunt for a move by feel. With a hardware keyboard, arrows or WASD roam a cursor and Return places and commits.
- Free play offers unlimited undo and all the variants; the daily is one attempt at the day’s shared board, one undo per move.
- The chart under the board shows your position’s openness — legal moves available — against your best game’s curve. Stay above the ghost.
- The rules are in the app too: the ? button on the board.