Pipe Placement Mode
- Highlight all tiles with pipes on them and in the current "pipe layer"
- When placing pipes it would place the next obvious pipe.
If the mapper connects a straight horizontal and vertical pipe path then it should make the intersection a + pipe.
The mapper should also be able to place a pipe on an "elevated layer", which simply would mean that all other pipes shouldn't be considered except pipes on this layer.
The layer is just an abstraction.