Editing Linked portal (section)

===Setting up sector portals===
There must be (at least) two sectors in the map, not linked together by any path (similar to how disjoint areas exist in classic Doom maps and are gameplay-connected only by teleporters).

The ceiling height of one of them must match the floor height of the other. Let's call the bottom sector A and the top sector B.

Even though the sectors need to have the same outline, they can have different detail inner sectors in them. For example, sector A can have several crate sectors whose outlines don't need to be copied into upper sector B, which has much less detail. Note that one-sided linedef walls inside sectors (e.g. columns) must have their outlines copied.

Reserve two linedefs for each sector. Make sure the two linedefs selected for sector A will have the same relative coordinates and sizes as the two corresponding linedefs from B.

Tag sector A and its inner details with a number. Tag B and its details with another number.

Give the reserved linedefs from A special 359, tag of B and special 360, tag of A respectively. Give the reserved linedefs from B special 358, tag of A and special 361, tag of B respectively. Here is how they should correspond:

* Reserved linedef 1 of sector A: special 359, tag B (Apply linked portal to floor of B)
* Reserved linedef 1 of sector B: special 361, tag B (Linked portal anchor line for special 359)
* Reserved linedef 2 of sector A: special 360, tag A (Linked portal anchor line for special 358)
* Reserved linedef 2 of sector B: special 358, tag A (Apply linked portal to ceiling of A)

Note that with this implementation, you'll have to give a tag to every sector which needs a portal. Sometimes this is not practical, because you may want to make various sectors with special effects within A or B. To bypass this problem, you can tag the special sector differently, but one of the linedefs facing it must have special 385 (Apply portal to front sector) and have the tag of the non-special sectors that surround it (A or B). This will copy the portal information into the special sector.

Here is a diagram on how to set up:

 :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
 -----------------x---------------------x:::::::::::::      ~-------------------x---------------------x:::::::::::::::::::
                 /                       \::::::::::::      ~ Neighbour        /                       \::::::::::::::::::
  Neighbour     /         SECTOR A        \::::::::::       ~ sector of       /         SECTOR B        \:::::::::::::::::
  sector of    /  x----x             floor \:::::::::       ~ B              /  x----x                   \::::::::::::::::
  A           /   |::::|             detail \::::::::       ~ (not tagged)  /   |    |                    \:::::::::::::::
  (untagged) /    |::::|wall         x---x   \:::::::       ~              /    |    |top of wall from A   \::::::::::::::
 -----------x     x----x             |   |    x:::::::::    ~-------------x     x----x <NOT tagged          x:::::::::::::
 ::::::::::::\                       x---x   /:::::::::::::::::::::::::::::\                               /::::::::::::::
 :::::::::::::\    x---x-----x same tag as^ /:::::::::::::::::::::::::::::::\     x-------------x         /:::::::::::::::
 ::::::::::::::\    \   \    | <  A        x:::::::::::::::::::::::::::::::::\    x-------------x        x::::::::::::::::
 :::::::::::::::\    x---x---x            /360,A::::::::::::::::::::::::::::::\ ceil. detail            /358,A::::::::::::
 ::::::::::::::::\ flr.detail    359,B   /:::::::::::::::::::::::::::::::::::::\ tag of B      361,B   /::::::::::::::::::
 :::::::::::::::::x-------------x-------x:::::::::::::::::::::::::::::::::::::::x-------------x-------x:::::::::::::::::::
 :::::::::::::::::::::::::::::::::THE PORTAL LINEDEFS:::::::::::::::::::::::::::::::::::::::::THE PORTAL LINEDEFS:::::::::