Care to guess the arrangement of the next puzzle in this series? It’s surely a square grid of cells, right? In the case of Magnets, not exactly: instead, it looks more like a pattern of dominos. Each one takes up two cells of an invisible, underlying grid, and there are no unpaired cells.
Each segment is either empty, or a magnet. Here’s the interesting part – if a segment contains a magnet, it has to obey the laws of magnetism. Its positive pole can’t be adjacent to any other positive poles, and likewise for the negative ones. Clicking on a magnet already placed either flips it around, or removes it. Guesses placed incorrectly will be highlighted, as with other puzzles in the Simon Tatham collection.
Right-clicking a segment marks it empty, with X’s and a green background. These don’t affect the magnetic poles at all, so magnets can be placed next to them in any orientation. That’s where it gets tricky – most puzzles contain more empty segments than it would seem.
The clues along the left and top sides indicate the number of positive poles in that particular row or column of cells. Those along the bottom and right sides indicate the same for negative poles. One key to remember here is that this doesn’t apply to entire magnets; only to the specific type of pole. If a row has three positives, for instance, it must contain at least three magnets. However, some of the other cells in that row might be negative poles; they don’t all have to be empty.
To get started solving one, first look for rows or columns marked zero. These don’t mean the entire row or column is necessarily empty; remember, it could still contain the opposite type of pole. The only segments that are safe to completely eliminate are ones that align with that row or column, since they could never contain half a magnet, or a magnet with only one type of pole. Placing one pole there means an opposite one comes along with it! Thus, in a row marked zero, only horizontal segments can be marked out, and only vertical ones in a column.
By the same token, a magnet can be placed; perhaps not in the correct orientation, but at least to mark that segment as not being empty. If, for example, a column marked with two positive poles only has two vertically aligned segments, both must contain a magnet, regardless of how the magnets are oriented. Place the magnets, then worry about how they are oriented later. Once every segment is marked as either a magnet or empty, it’s a simple endeavor to flip them all the right way around.