Tracks
Lay a railway from A to B that matches the numbers on every row and column
Click or tap the edge between two squares to lay track there, and again to remove it. Right-click, Ctrl-click or long-press an edge to mark it as no track. Click the middle of a square to mark that it holds track, or right-click it to mark no track. Drag along a row or column to mark a line of squares as track, or right-drag to mark them no track; a drag that starts on a marked square clears the line instead. With the keyboard, arrow keys move between square centres and edges; Enter lays or clears track and Space marks or clears no track. The Selected square or edge buttons do the same for the focused one. Ctrl or ⌘ Z undoes and Shift Ctrl or ⌘ Z, or Ctrl or ⌘ Y, redoes while the board has focus.
Arrow keys move between square centres and edges. Enter lays or clears track, Space marks or clears no track.
Progress saves on this device.
How to play
Lay a railway from A, on the left edge, to B, on the bottom edge. The numbers above and to the right of the grid say how many squares in each column and row the track passes through. Track runs straight or turns a right angle in a square, never branches and never crosses itself. Some squares come with their track already laid; they are framed and cannot be changed.
Track that forms a loop or, once A and B are joined, lies off the route turns red, with dashed rails and a dashed frame round its square. A number that can no longer be met turns red inside a dashed ring. Marks for squares that hold track or no track, and crosses on edges, are notes that help you count. The puzzle is solved when one route joins A to B and every number is met.
Undo and Redo follow your history; a new move after Undo replaces the undone moves. Restart clears the board and can be undone. Solve reveals the answer; a puzzle finished with Solve does not count as solved.
Engine: Simon Tatham’s Tracks, contributed by James Harvey, from the Portable Puzzle Collection. MIT license and credits.