What is Train Tracks?
Train Tracks - often just called Tracks - is a logic puzzle in which you lay a single railway line across a square grid. Every cell is either empty or holds one piece of track, and each piece is either a straight (running across or up and down) or one of four curves (a quarter turn joining two neighbouring sides). Two pieces are printed for you at the edges: an entrance, where the line runs off the grid, and an exit somewhere else on the border. Your job is to connect them with one continuous track.
What turns it into a puzzle are the numbers along the right side and the bottom. Each number is a count: it tells you exactly how many cells in that row, or that column, carry a piece of track. Put the two ideas together - one unbroken line from entrance to exit, and the exact number of track cells in every row and column - and the whole route is forced. There is only one way to lay the rails.
- Each cell is empty or holds one track piece: a straight or a curve.
- An entrance and an exit are fixed on the border of the grid.
- Connect them with one continuous, unbranching track.
- Numbers on the right count the track cells in each row.
- Numbers on the bottom count the track cells in each column.
- Every puzzle has exactly one solution, reachable by logic alone.
How to play Train Tracks online
Click or tap a cell to drop a piece of track, and click again to rotate through the six pieces - the two straights and the four curves - before cycling back to empty. The entrance and exit pieces are fixed and cannot be changed. Right-click a cell to pencil a small cross when you are sure it stays empty; it never changes the puzzle, it just records your reasoning. The numbers along the right and bottom turn green the moment a row or column reaches its count, and red if you place one piece too many.
Check looks over your board and flags any piece that disagrees with the unique solution, without telling you which way it should face. Hint drops one correct piece into place - or clears a wrong one - Undo steps back through your moves, Reset clears everything you have drawn, and Solution lays the whole route when you would rather study it than finish it. New puzzle builds a fresh board for the size and difficulty you have chosen.
- Tap a cell to add a piece; tap again to rotate through the six pieces.
- The entrance and exit pieces are fixed and can't be changed.
- Right-click a cell to mark it empty; it is just a note for you.
- Row and column numbers turn green when met, red when overshot.
- Check, Hint, Undo, Reset and Solution help when you get stuck.
The counts are your compass
The numbers around the edge do most of the heavy lifting, and the extremes are the place to start. A 0 means a row or column holds no track at all, so you can rule the whole line out at a stroke. At the other end, a count that equals the width of the grid means every cell in that line carries track - fill it straight in. Most lines sit between the two, but even then the count is a hard budget: once a row has its number of pieces, every other cell in it is empty, and once a row is one piece short with a single candidate left, that cell must be track.
The real power comes from reading rows and columns together. A cell only becomes track if both its row and its column can still afford it, so a column desperate for pieces crossing a row that is already full pins that cell as empty - or the reverse forces it to be track. Sweeping back and forth between the row counts and the column counts, tightening each against the other, is how a board that looks blank turns into a board where whole stretches of track are suddenly certain.
- A 0 means the whole row or column is empty - rule it out at once.
- A count equal to the grid width fills that line completely.
- When a line reaches its number, every other cell in it is empty.
- A line one short with one candidate left forces that cell to be track.
- Read rows against columns: each count limits the other.
Follow the track from the ends
Because the entrance and exit are fixed, you always have two loose ends to build from, and a railway can only grow one way: each new piece must connect to the one before it. Follow the line inward from the entrance and the exit, and very often the next piece has only one legal shape - the neighbouring cell it must join to is already decided by a count, or every other direction is blocked by a full line or the edge of the grid. Growing the track from both ends until they meet is the most natural way to solve.
Curves and corners are especially talkative. A piece in the corner of the grid can only be one kind of curve, because two of its sides face off the board. A cell whose row or column is nearly full often has only one neighbour it can possibly connect to, which fixes whether it is a straight or a curve. And whenever a piece would force the line to leave the grid somewhere other than the exit, or to double back into itself, that shape is illegal - which usually leaves just one piece that fits.
- Build inward from the fixed entrance and exit pieces.
- Each new piece must connect to the track already laid.
- A corner cell can hold only the one curve that stays on the grid.
- A nearly full row or column leaves a cell only one way to connect.
- Grow both ends until the two stretches of track meet.
No branches, no loops, no loose ends
Train Tracks is a path, not a maze. The finished line is a single continuous route from the entrance to the exit, which means every track cell connects to exactly two things: the piece before it and the piece after it. There are no junctions where three rails meet, no level crossings where two lines pass through one cell, and no separate loops floating off on their own. The only two places the track touches the border are the given entrance and exit.
That single-line rule is a constant source of deductions. A piece that would create a fork is illegal, so is one that would close a small loop back on itself, and so is one that would leave a stub of track with a dead end going nowhere. Whenever a count or a corner offers you two possible pieces, the no-branch, no-loop, no-dead-end rule almost always rules one of them out. Keeping the line single and unbroken is as much a solving tool as the numbers are.
- The track is one continuous path from entrance to exit.
- Every track cell connects to exactly two neighbours.
- No forks, no crossings, and no separate loops.
- No dead ends - the line never stops in the middle of the grid.
- Use the single-line rule to reject pieces the counts allow.
Where Train Tracks comes from
Train Tracks is a more modern arrival than the classic Japanese pencil puzzles, and it spread through newspapers and puzzle apps rather than the Nikoli magazines that gave us Sudoku and Slitherlink. It is best known simply as Tracks, the name under which it runs as a daily feature in several newspapers, and it has appeared widely in puzzle books and collections, including those of the prolific puzzle author Gareth Moore. The railway theme - an entrance, an exit and a single line to be threaded between them - has made it an easy puzzle to pick up and a popular one to set.
Underneath the trains, the idea is elegant and surprisingly deep. Counting clues around the edge are an old device, shared with Nonograms and Magnets, but combining them with a single continuous line gives Train Tracks a flavour all its own: part counting puzzle, part path-drawing puzzle. That blend, and the friendly visual of laying rails between two stations, is why it has travelled so well from the newspaper page to the phone screen.
Train Tracks vs Slitherlink, Masyu and other line puzzles
Train Tracks belongs to the family of line-drawing puzzles, but it draws a path rather than a loop. In Slitherlink you read numbered cells and join dots into exactly one closed loop; in Masyu you thread a single loop past black and white pearls. Train Tracks asks for an open line instead - it has two ends, the entrance and the exit - and it is steered by counting clues along the margins rather than by numbers inside the grid. The instinct of following forced connections from a fixed point, though, is exactly the same.
Compared with the counting puzzles it borrows from, Train Tracks feels more geometric. Nonograms and Magnets count along rows and columns too, but you are shading cells or charging dominoes; here you are choosing the shape of a rail and keeping a line connected. That makes it a friendly bridge: if you enjoy the forced-move chains of Slitherlink you will feel at home, and if you have only ever counted your way through Nonograms, Train Tracks is an easy and rewarding way to start thinking about connected paths.
- Slitherlink: clues count edges; you build exactly one closed loop.
- Masyu: thread a single loop obeying black and white pearls.
- Nonograms: edge counts, but you shade cells rather than draw a line.
- Train Tracks: edge counts plus a single open path from entrance to exit.
- It bridges counting puzzles and path-drawing puzzles.
Grid sizes and difficulty levels
The 6x6 boards are the place to learn the moves: a short railway, counts that are easy to picture, and forced pieces that follow quickly from the entrance and exit. On 7x7 the line gets longer, more rows and columns share their counts in awkward ways, and you lean harder on reading rows against columns. The 8x8 boards are full puzzles - a long, winding track, counts that interact right across the grid, and stretches where you must follow the line and the numbers together before a single piece is sure.
Difficulty changes how many track pieces are revealed to start. Easy boards show plenty of the route, so each new piece follows from a short, local deduction and the track grows steadily. Medium reveals fewer pieces, leaving more of the line to be reasoned out from the counts. Hard shows little beyond the entrance and exit, so you work the counts and the single-line rule against each other for longer before the railway takes shape. Whichever you choose, every board is checked by a solver before you see it and only those with exactly one solution are kept - so each puzzle is always solvable by pure logic, never by guessing.
- 6x6 - a short track and gentle counts to learn the rules.
- 7x7 - a longer line and more interplay between the counts.
- 8x8 - a winding track and deductions that cross the whole grid.
- Easy, medium and hard change how many pieces are revealed.
- Every puzzle is verified to have exactly one solution.