Trail

Expert Trail puzzles

Expert puzzles are 8×8 and 9×9 and need the longest chains of forced moves. Plan the stretch between two numbers as a whole, and keep an eye on which cells each choice would leave stranded.

Practice gives you puzzles you haven't solved yet, as many as you like, and keeps your best time without hints. Every puzzle has exactly one solution and can be solved by logic alone.

How to play Trail

1. Start on the 1 and draw a single trail that goes through every cell exactly once.
2. Pass the numbers in order: 1, then 2, then 3, and so on. The trail ends on the last number.
3. Move up, down, left or right, never diagonally, and never through a thick wall.

Drag from the 1 to draw, or tap the cells one at a time. To erase, go back the way you came: the trail shrinks a cell at a time. Brushing past any other part of the trail does nothing, so a slip never costs you progress. To jump further back, tap a cell on the trail to cut it back to there, or undo. On a keyboard, move to the end of the trail and use the arrow keys to draw, Backspace to step back and Ctrl+Z to undo.

Solving tips

• Mind the corners. A corner cell has only two neighbors, so the trail has to come in through one and leave through the other. The same goes for any cell that walls or the trail have boxed in.
• Don't strand a cell. If you pass right next to a cell that has only one other way in, you must go into it now. Leave it for later and the trail can never come back for it.
• Don't cut the board in two. If your trail splits the empty cells into separate areas, it can only ever reach one of them.
• Head for the next number. Every cell you skip on the way has to be picked up later, before the trail reaches the numbers that come after.