Look at the tiles marked in red below: Their lines run into an edge of the puzzle. This can't be right. The tiles must be turned in such a way that all the tile lines continue on other tiles or else the lines can't end in a diode. So no tiles can have lines on them that run into a puzzle edge.
For example, take the tile that has been marked in the
rightmost column in the picture above. It can only be turned in one of two ways:
or
.
All the other orientations make the line run into the puzzle edge.
Now consider the
top left tile that has been marked in the top picture above:
The
only way it can be turned is
.
All the other orientations make its line run into the puzzle edge.
... so the tile to the right of it is okay (its line doesn't run into the puzzle edge and it also joins the line on the adjacent tile)
... but the then following tile is
not okay it doesn't join a tile that we know is okay).
So let's turn that latter tile into the only orientation that matches the tile to the left: We get
.
But now the tile that follows
then can't be right: For one, it runs into the puzzle edge, and for another, it doesn't match its left neighbour...
.
Poll
