Authors Strategy - Door Puzzle - level 21

   This page contains three sections. The first details how the automated doors work, the second describes a bug. The third section gives advice and briefly outlines the strategy I used to complete this mission.

How the doors work...

	Generally speaking, each room is connected to it's neighbouring rooms by two doors. If the player has units in a room all the doors connecting that room to it's neighbours will open (and will remain open until all the player units have left the room). It therefore follows that each group of two doors has an detection area defined by the two rooms those doors connect and by the areas the doors themselves occupy.    If you don't find this description very clear, have a look at Fig.1. The area defined by the green box is the detection area for doors B and C. Whilst the player has units inside the green box doors B and C will be open.
	The detection areas described above will obviously overlap each other. In Fig.2 the marine is in the detection area for 4 pairs of doors (leading to rooms A, B, C and D). As a result all these doors are open.
	In Fig.3 the marine has moved north into a doorway. He has now moved out of the detection areas for the doors leading to rooms A, C and D (not shown). As a result, the doors leading to these 3 rooms have closed. The marine is still in the detection area for the doors leading to room B, so these doors remain open.
	Fig.4 shows the final room. If any player unit is inside the area defined by the green box at the end of a turn all the doors will open. Once this happens the doors lock in the open position and will not be active for the remainder of the mission.

A Slight Bug ?    If a marine steps into an area, and as a result a door is lowered to reveal a Scay'Ger, the Scay'Ger may still appear as a scanner blip until the next player movement has been made.    I suspect this is due to the positioning in the Incubation code of the routines for determining line of sight. It would seem that the Inc engine calculates which enemy units are visable immediately after a player has moved a unit, but before LCL commands are executed.    Confused? Then look at Fig.5. Here a marine has moved into area A causing the doors at B and C to open. The sequence of events is as follows; the marine moves, the Inc engine then assesses the line of sight and determines that the player cannot see the Scay'Ger (the door at B is in the way). The LCL code is then executed and doors B and C are opened (lowered into the ground).    The Scay'Ger will not become visable to the player until the next line of sight assessment is made. This will occur when a player unit is next moved. The situation shown in Fig.5 can be avoided by moving the marine in two stages. If the marine is moved south into area A the doors will open (but the Scay'Ger will not be 'visable'). The marine is then moved one space east to his final position, this causes another line of sight assessment, the Scay'Ger will now be visable.    I have playtested this mission about 10 times, and although this line of sight problem has occured on several occasions, it has never really effected the gameplay. Not so much a bug, more like a quirk due to the order in which Incubation carries out its line of sight assessment (or whatever).    Of course, my theory about why this happens could be completely wrong.....

Strategy Tips

   There are two equipment crates in the mission area, one to the north of your starting position, one to the east. Both of these crates contain coolers. I sent my three marines east and was able to obatin the cooler in the eastern crate by turn 3 or 4. As you progress to this crate doors will open revealing some Gore'Ther. Don't worry about these, they are slow and it is likely that they will be trapped as the doors close behind you. A few Ray'Coo will jump into combat, but these shouldn't present you with too much of a problem.
   After obtaining the first cooler, head west and then diagonally across to the northern crate. As you make this journey you will have to out manouver some Gore'Ther, and if done correctly, you should be able to kill one or two of them (if you don't do this you're going to get into some tight situations later on in the mission). As you approach the northern crate more Ray'Coo will jump into combat. If your pointman is the chainsaw guy you will not be troubled by these too much.
   Grab the cooler and head east. Be careful! There are two rooms containing Dec'Ther. If you stumble into a detection area for the doors to either of these rooms you're not going to last long. Be sure that when you approach these areas you are able to place at least one of your doublefire guys (prferably both) on defensive fire. After grabbing the second cooler I dealt with the first group of Dec'Ther and then moved further east towards the center of the mission area.
   As you approach the center (and the air vent/Scay'Ger hole) a lot of Ray'Coo that have been ammassing will jump to surround your marines. Your chainsaw guy should again be at the point (or very close to the pointman). If one of the doublfire guys is isolated and becomes surrounded by Ray'Coo he isn't going to last long.
   Once you marines have entered the exit room all the doors will open permanently. This will give you a big headache if you haven't dealt with the second room of Dec'Ther. You will find yourself trying to not only out manoveur the Gore'Ther in the final room, but you will also have to deal with the Dec'Ther (not an ideal situation). So, before entering the final room, I headed east and took out the second room of Dec'Ther.
   Then it was on to the final room. Once you are in the final room (and all the doors have opened) a few Dec'Ther will emerge from the air vents/holes in the north-west and south-east corners. If you move quickly to the red area (marked A) they shouldn't be able to catch up with you. But if you hang around....

Note: You may feel you don't need to get the coolers, you may be right! But obtaining them means that you're unlikely to run hot when defending against the Dec'Ther.