Ignore the lines and diodes on the middle of the tiles for the moment. Realize that in order to yield unbroken lines, the **edges** of adjacent tiles must match Within the middle of a tile, the lines could run any old way; what matters is just where these lines end on the tile **edges**. Adjacent tiles need to be oriented in such a way that the touching **edges** match.

How to use this for finding out how the tiles need to be oriented:

1. Consider the outer puzzle edges first: They don't feature any line ends. So tiles that are next to a puzzle edge can only be oriented in such a way that no lines run up to the puzzle edge. For many tiles that means that they can only be oriented in one way or two ways.

2. Note that the puzzle has a "hole" in the middle, which is a puzzle edge, too. Tiles that are adjacent to the "hole" can only be oriented in such a way that no lines run up to the "hole".

3. Now consider the tiles that are adjacent to some tile where you already **know** its orientation. These tiles must be turned in such a way that their touching edges match the respective touching edge of the known tile. Again, in many cases there will be just one possible orientation. Now work your way iteratively through the puzzle.