MAP24: Detachment (Community Chest 4)

MAP24: Detachment is the twenty-fourth level of Community Chest 4. It was designed by Matt Devlin (Shadow Dweller) and uses the music track "Death's Bells" from MAP04 of TNT: Evilution.

Essentials
This level is characterised by being atmospheric - in short, there's a serious lack of light in this level, and it does pack more than a few surprises. A highly detailed mix of a base and hellish elements, featuring a cyberdemon encounter amidst bombed-out ruins, this level will keep you on your toes from start to finish.

Start and Red Key

You begin on a helipad. Make your way north to the entrance of the base - it's quiet for now. Head through the gate of the base and clamber up onto the pile of crates in the courtyard to get a super shotgun. As you do so, you alert three groups of monsters: up to six imps behind the crate, up to four imps on a platform in the east, and a group of four demons in the west (with an arachnotron on Ultra-Violence and above). Use the barrels and monster infighting to your advantage. Once that is done, collect the backpack behind the pile of crates and head to the platform in the east for a box of ammo and a box of shells.

Head to the west side of the entrance courtyard. Go through the hole in the fence and open the door that is slightly ajar. This darkened room contains an armor. As you enter, you will be ambushed by an imp, a shotgun guy and up to two zombiemen. For now, you can't any door other than the one in the southeast of the room, so open that one. it leads to a corridor with up to four shotgun guys and five imps (no imps on Hey, not too rough and below). Mow them down and open the door at the end of this corridor.

This next large room is empty. Flip the switch in the northeast corner to open the blast doors in the north. Up to three cacodemons will attack. Head into the room where they came from and collect the chaingun and light amplification visor from the scattered crates in the northeast, then head through the door in the west. This next room has up to six imps. On Ultra-Violence and above, one is in an ambush position right next to the door and one is hidden behind a computer block right of the door, so be careful. At the southwest end of this room is the red key, which you can easily take.

Unlocking the Second Half

Exit the red key room, open the blast doors and head south. The red door is in the southeast corner. Go through it to a long corridor with two (Hey, not too rough and below), four (Hurt me plenty) or eight (Ultra-Violence and above). Further up, the corridor is blocked by rubble. Head right (east) to a rocky area with up to six imps, four shotgun guys and four lost souls. As you step into this area, the rock pillars in the room lower, revealing a mancubus and two revenants - make them infight.

From the rocky area, head north into another corridor, this one running east-west. The middle of this corridor is blocked off by rubble. Head west and clear out the imp and up to five shotgun guys firing from behind the rubble. To get around the rubble, go up to it, then detour to the right (north) into a brown rocky area (watch for three zombiemen here). After going around the rubble, head through the red door in the south.

You will now enter a large room with a force field at the western end. This room houses the level's first big fight. As you enter, you are set upon by three groups of monsters - up to three imps in front of you, a lance of up to three zombiemen, a shotgun guy and an imp in the southeast corner, and the main horde of up to nine imps, four shotgun guys and two chaingunners in the west. Quickly maneuver around them and try to get the rocket launcher in the west. Once the room has been cleared out, climb out to the computer terminal in the southwest, flip the switch and hurry to the eastern side of the room.

The force field deactivates, as planned, but shortly after, the room is racked by the sound of explosions and the western half begins to undergo a drastic transformation. A large section of the floor and computer terminals collapses into a channel of lava, leaving only stepping stones to get across. Monsters begin teleporting into the room. Shortly later, a rock pedestal rises out of the lava, and a tough monster teleports onto it. If you're counting kills:


 * Hey, not too rough and below: Three cacodemons, revenant on pedestal
 * Hurt me plenty: Three cacodemons and two Hell knights, arch-vile on pedestal
 * Ultra-Violence and above: Three cacodemons, a pain elemental, six lost souls, two barons of Hell and two Hell knights, arch-vile on pedestal

Fight to survive this tough battle, then make your way to the western half of the room that was formerly behind the force field. Climb up the steps, flip the switches on either side to release the bars, then flip the lever in the middle. The red lights behind the lever will become green.

Blue Key

At the left (south) switch, note that part of the wall at the corner is damaged. Sidle through this damaged area to get to a room with a Hell knight and a baron of Hell (Ultra-Violence and above only). On Hurt me plenty and above, there are up to four imps waiting in ambush near the computer block you emerge next to, so be alert. Flip the switch in the southeast to open a door leading back to a room right at the entrance of the base. The door in the southwest is opened and surrounded by green lights - head through it to a U-shaped set of corridors - one flat, one with steps going up. Detour to the flat corridor to access a room containing up to two demons and a spectre, but more importantly a megasphere - you'll need it very soon.

Backtrack, then head up the corridor with the steps and open the door at the top. You will be set upon by three shotgun guys and two imps (not on Hey, not too rough and below). However, the real problem is visible through the holes in the wall - the huge horde of enemies in the ruins outside. In total, the following enemies are out there:


 * Hey, not too rough and below: Two cacodemons, three shotgun guys, two demons, two imps.
 * Hurt me plenty: Four cacodemons, six shotgun guys, three revenants, two demons, two spectres, four imps.
 * Ultra-Violence and above: Six cacodemons, nine shotgun guys, four revenants, six lost souls, four demons, four spectres, four imps.

Hop out the wall, grab the plasma gun and get to work. Proceed east through the ruins. As you enter the eastern section, the wall in the east collapses, revealing a cyberdemon and other monsters:


 * Hey, not too rough and below: Just the cyberdemon.
 * Hurt me plenty: One cyberdemon, four revenants and an arachnotron.
 * Ultra-Violence and above: One cyberdemon, eight revenants and two arachnotrons.

This will get messy. Unlike other cyberdemon fights where you had to circlestrafe or micrododge, in this one you'll need to play a nasty game of hide and seek - and you'll need to be precise to get through the ruined walls. Once the monsters have been dispatched, head to the area in the east where they came from to collect the blue key.

Yellow Key and Exit

In the exact south of the ruins is a blue door - use your blue key to get out. On Hurt me plenty and above, you will immediately encounter a mancubus, which will use invisible teleport lines to teleport behind you. Head through the door and kill the imps in the cages next to the second blue door. Go through this second blue door.

This next large room has a brown central structure. You will first encounter up to three groups of monsters - four shotgun guys in the west, up to four imps in the southeast. On Hurt me plenty and above, there is a group of Hell nobles too - two barons of Hell on Hurt me plenty, two barons of Hell and two Hell knights on Ultra-Violence and above. Defeat all the enemies and proceed to the west side of the room. The yellow key is behind the western pillar. However, stepping onto the base of that pillar (this includes collecting the nearby rockets!) will open up the central structure, revealing the following enemies:


 * Hey, not too rough and below: Two revenants.
 * Hurt me plenty: Four revenants.
 * Ultra-Violence and above: Four revenants and an arch-vile.

Dispose of them with your rocket launcher, then leave the room to the corridor where the mancubus was before it teleported. In the east of this corridor is a yellow door. Open the door to reveal a room with a computer system, a blocked off structure in the south and a good number of enemies:


 * Hey, not too rough and below: Three zombiemen, two imps.
 * Hurt me plenty: Three zombiemen, two imps, two shotgun guys.
 * Ultra-Violence and above: Three zombiemen, four imps, four shotgun guys, two Hell knights and two mancubi.

Head up to the raised floor with the computer system and flip the switch to unblock the structure in the south - it is a teleporter. Before you can use it, a few enemies come out - two lost souls (Hey, not too rough and below), five lost souls (Hurt me plenty), or five lost souls and an arch-vile (Ultra-Violence and above). Dispose of them and step into the teleporter to be teleported to the final stretch of the level.

In this last stretch, all you need to do is follow the winding path. On Hurt me plenty and above, you start out attacked by a pack of lost souls - seven on Hurt me plenty and 11 on Ultra-Violence and above. Further along the path, you meet a two lost souls (Hey, not too rough and below), three Hell knights (Hurt me plenty), or three Hell knights and a baron of Hell (Ultra-Violence and above). At the end of the path, your last opposition is a group of up to six demons and four revenants.

Flip the switch in the east of this last area to exit the level.

Secrets

 * 1) Directly behind your start you can get an armor and a berserk pack. (sector 1)
 * 2) Open the red door and take the hallway until you can branch off into either a cargo bay or a rocky cutout. Go into the cargo bay and maneuver through the crates to the southwest corner to find a switch. This lowers a crate in the center of the cargo bay, where you can cross into a secret with a plasma gun, health bonuses, a box of shotgun shells, energy cells, and a backpack. (sector 1643)
 * 3) Head through the rocky cutout mentioned above and into another tech hallway. Near the door with health bonuses in front, press on the computer panel to reveal a door. Open it to get a megaarmor and various ammo boxes. (sector 1858)
 * 4) In the final area, just before the exit switch, spot a tiny ledge to the south which you can use to get onto the rocks. Head around for a medikit, a stimpack, and armor bonuses. (sector 1661)

Current records
The records for this map at the Doomed Speed Demos Archive are:

Miscellaneous demos
''This information was last verified in its entirety on January 23, 2018.

Player spawns
This level contains eleven spawn points:
 * 1) facing north. (thing 895)
 * 2) facing north-west. (thing 896)
 * 3) facing south-west. (thing 897)
 * 4) facing south. (thing 898)
 * 5) facing east. (thing 899)
 * 6) facing north-east. (thing 908)
 * 7) facing north-east. (thing 909)
 * 8) facing north-west. (thing 925)
 * 9) facing south. (thing 926)
 * 10) facing west. (thing 953)
 * 11) facing south-west. (thing 963)

Things
This level contains the following numbers of things per skill level:

Technical information
Simulated Slope

Near the start of the level, there is a slope leading up a platform. This is simulated by having many thin sectors in a staircase pattern. To enhance the illusion, the floors and lower textures use a flat and texture with an identical pattern ( and respectively).

Blast Doors

Near the start of the level, flipping a switch causes a blast door to open - its upper segment raises up and the lower segment lowers. This simultaneous action of floor and ceiling is accomplished using two voodoo dolls in a repeatable action setup.

Two voodoo dolls are placed in scrolling control sectors, each blocked from scrolling forward by a lowered portion of ceiling (the "blocker sector"). The two lowered ceilings are joined to be a single sector. Flipping the switch causes the following to happen:


 * First, the ceiling of the blocker sector raises, allowing the voodoo doll to move forward.
 * Simultaneously, one voodoo doll crosses a line causing the ceiling of the blast door sector to raise while the other crosses a line causing the floor of the blast door sector to lower, opening the blast door.
 * A bit later, one voodoo doll resets the blocker sector to its lowered state.
 * After some delay, one voodoo doll crosses a line causing the ceiling of the blast door sector to lower while the other crosses a line causing the floor of the blast door sector to raise, closing the blast door.
 * Using a silent teleport line, both voodoo dolls are teleported to their initial positions. With the blocker sector re-lowered, they cannot scroll forward.

Drastic transformation of room

About halfway through the level, the player flips a switch and a room undergoes a drastic transformation, with the floor sinking into a lava river and rocks appearing. This effect is achieved with voodoo dolls in a manner far simpler than it looks.

The room has been divided into sectors corresponding to the parts that need to sink completely into lava, and the parts that need to sink and re-raise. Each part is joined to a control sector, which is in turn adjacent to another control sector at a lower floor height. Parts that need to sink completely are next to a single control sector; parts that need to sink and re-raise are next to two control sectors.

Flipping the switch in the room merely sets two sets of voodoo dolls in scrolling control sectors into action. Each then steps over a large number of walkover linedefs in sequence, first sinking the sectors with generalised floor actions "W1 lower to lowest floor; fast; change texture and effect". When this is done, a third voodoo doll in its control sector is set into motion. The sectors that need to be re-raised are raised with generalised floor action "W1 raise to next higher floor; fast; change texture and effect"

Of note is that to avoid problems with the numeric model and linedef numbering, the trigger model has been picked. However, this necessitates damaging floor sector flags on the sector on the back of the trigger line. To avoid damaging the voodoo doll (and the player), the damaging sectors are thin and deeply sunk, so the voodoo doll simply steps across them, never touching the floor.

Room Over Room - Straight Corridor

In the west side of the level, a room over room implementation simulates visiting a room under the staircase, and visiting a second half of the level that is above the first half. This is accomplished using a standard implementation of Boom's silent teleporter (action 244 - WR Silent Teleport to Line with Same Tag).

The implementation in this level is unusual as it is performed with a straight corridor and a straight staircase (instead of a spiral staircase) where the sight lines are longer. However, since that area is completely free of things, the two identical sections of the level can easily remain identical and the illusion is preserved.

Trivia
In one of the rooms with a grated floor flat, there is a bloodstain on the floor (sector 230). In accordance with what would be expected in reality, the holes are blood-free. However, the bloodstain is not a floor with a red-tinted version of - rather, the bloodstain is a standard red flat. Instead, since flats are aligned with a 64x64 grid, small rectangular sections corresponding to the holes in the grated floor flat have been meticulously cut out from sector 230 (collectively sector 208), with these sections being given the floor flat to give them the appearance of holes.