This is an example starting grid. We have been given some starting pieces of track, but most are missing.
The first task on any TrainTacks puzzle is to look for rows and columns that are already complete, i.e.
where the clue is satisfied. If we look at the first column from the left, we can see that clue is '1',
so we can fill the rest of the cells in that column with a 'X'.
The second task for this puzzle is to mark all the implied cells. These are cells where there is a piece
of track that 'points' to that cell. We don't know exactly which piece of track will be in these cells,
but we know they will contain a piece of track, so we can mark them as being occupied.