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A logic puzzle from Simon Tatham's collection. Every cell holds an arrow, and you must thread one path through all 36 cells, numbered 1 to 36, so that each arrow points at the next number somewhere along its line. A few numbers are given. Every 6×6 board is generated fresh with exactly one solution, and your time is your score.
Every cell on the 6×6 grid has an arrow pointing in one of eight directions, except the last cell, which shows a star. Your job is to number all 36 cells from 1 to 36 so that the arrow in cell 1 points at cell 2, the arrow in cell 2 points at cell 3, and so on. The next number can be any distance away, as long as it lies on the straight line the arrow points along. Some numbers, always including 1 and 36, are given and cannot change.
To link two cells, tap the first one and then tap a cell that its arrow points to. The cells its arrow can reach are highlighted while it is selected, and after a link the new cell stays selected so you can keep going. You can also drag from one cell to the other. Tap a selected cell again to break its outgoing link.
A chain that touches a given number is numbered automatically. A chain that has no number yet is shaded in its own colour and labelled with a letter, such as a, a+1, a+2, so you can build pieces of the path before you know where they go. If a chain's numbers clash with a given number, or two cells end up with the same number, they turn red.
The clock starts when you press Start and stops the moment all 36 cells form one correctly numbered path. Every board has exactly one solution, and your time is your score.
Look at both ends first. Cell 1 has nothing before it, and the star cell has nothing after it. Then work backwards from the star: find every cell whose arrow runs through it. If only one does, that cell must be 35, and you can repeat the question for 35.
Every cell except 1 needs exactly one cell pointing at it, and every cell except the last needs exactly one place to go. So hunt for cells with a single option either way. A cell near an edge whose arrow points toward that edge often reaches only one or two cells, and a corner cell may lie on the line of just one arrow. Each forced link removes options from its neighbours, and a board usually unravels from a few of these.
Given numbers with a small gap between them are the strongest clues. If 12 and 14 are both on the board, 13 must lie on 12's arrow line, and 13's own arrow must point back toward 14. There are usually only one or two cells that satisfy both at once.
Build lettered fragments freely. A chain like a, a+1, a+2 that you are sure about will number itself the moment you attach either end to a known number, and a red number is an instant warning that a fragment has been placed where it does not fit.