E1M7: Computer Station (Doom)

E1M7: Central Processing is the seventh map of Knee-Deep in the Dead in Doom. It was designed by John Romero and uses the music track "Demons On The Prey". The par time is 3:00.

Walkthrough

 * Letters in italics refer to marked spots on the map. Sector numbers in boldface are secrets which count toward the end-of-level tally.

Essentials
From the start point (A), go through the door and take the first left. Follow the corridor to an alcove on your left (east), the far corner of which contains a lift (B). Go up this lift and follow the ledge around to a small technical room containing the yellow key.

Leave the alcove and bear slightly left (not up the blue staircase). If you play on Ultra-Violence or Nightmare!, watch out for the eight sergeants outside the window to your left (guarding the invisibility), some of whom may open fire as you pass. Go through the yellow door (C) into a computer room. Proceed straight ahead (west), turn the corner, and leave the room through the passage to the south. You will pass a blue door (D), then approach a wide curved staircase (E). As you reach the top of this staircase, the brown column in front of you will lower rapidly, revealing a sergeant (I'm too young to die and Hey, not too rough), or two sergeants (Hurt me plenty), or four sergeants (Ultra-Violence and Nightmare!).

Go around the column and bear right (northwest); follow the passage along through a yellow door and into a large octagonal room containing several barrels and a green armor. At the far end of this room is a lift (F), which leads to a gray passage containing the red key. As you round the turn in this passage, two traps will open elsewhere in the level (G, H), releasing a sergeant and a trooper (ITYTD and HNTR), or a trooper, a sergeant, two Imps, and a Demon (HMP), or a trooper, two sergeants, two Imps, and two Demons (UV and NM).

The red door is near the start point; you would have seen it if you had initially turned right instead of left (I). The blue key is on a balcony behind this door, but as you step onto the balcony, two traps will open elsewhere in the level (J, K), releasing two sergeants and an Imp (ITYTD and HNTR), or four sergeants and two Imps (HMP), or six sergeants and five Imps (UV and NM).

Return to the blue door, and ascend the staircase on the other side. Cross the rectangular room and enter the passage directly ahead. Follow the passage around to a recessed button in a dark room (L), which opens the gray door at the other end of the rectangular room (M). Go through the gray door to the exit room; if you play on UV or NM, watch out for the six sergeants outside the window on your right. Press the switch.

Other points of interest
As you cross the north side of the computer room, a lift will lower to your left (N). Use this lift to access the central area of the room, which contains a rocket launcher and a shell box.

The column trap near the curved staircase will rise again if you step onto it. By jumping off at the right time, you can land on the small ledge to the northeast (P), which leads to an alcove containing a computer map. (This maneuver is rather difficult, so you may want to save your game first. If the column rises without you, walk to the curved stairway to lower it again.  If you are still on the column when it reaches its maximum height, you are not trapped: the switch on the west wall lowers it again.)  As you pick up the computer map, a tiny bridge rises behind you, connecting the small ledge back to the column area. If you fall into the slime, run to the radiation suit in the back corner (Q), and then see secret #2 below.

If you take the left fork after passing the column, you will go through a door into a dark computer room (O) containing a bullet box and a rocket box. There is also a chainsaw here, though it is not immediately accessible (see secret #1 below).

Secrets

 * 1) If you use the rising column to jump into the nukage pool to the north, or if you fall off the ledge near the computer map, run to the radiation suit in the back corner (Q).  After picking up the suit, turn around and press the red switch behind you.  A small door opens to reveal a staircase (sector 153), at the top of which are a rocket box, two medikits, and a metal switch.  Pressing this switch opens the square column with the chainsaw inside (R).  To get out of the nukage, see secret #2 below.
 * 2) The north nukage pool must be exited by running to the extreme northern end, where there is a small platform (S) with a soul sphere.  As you step onto this platform (sector 71), a hidden door opens to your right, providing a shortcut back to the beginning of the level.  On your way through the nukage, you will also see a tall brown column on your right; concealed here is a small alcove (T) containing blue armor.
 * 3) If you instead jump from the rising column into the south nukage pool, you will find a thin concrete platform (U) containing a chaingun, several large ammo pickups, and a medikit (sector 147).  This platform also adjoins a narrow passage leading to a backpack.  As you reach the backpack, a hidden door opens to your left, returning you to the curved staircase.  Note that this nukage pool contains one armor bonus (V).
 * 4) One of the traps triggered by the blue key platform (K) contains a secret door on its east wall, indicated by a greenish texture.  This reveals a passageway (sector 94) leading to the large courtyard with the invisibility (W).

Bugs
Four barrels (Things 112, 113, 114, and 187) have no flags set for any of the three difficulty classes, so they do not actually appear in the level.

Linedef 450 has its upper texture on the wrong side, resulting in a Hall of Mirrors effect. This is not normally observed, however, because the corresponding sector (a tiny hidden area of height 8 near the rocket launcher) is inaccessible without cheating. Similarly, linedefs 744, 745, 746, and 747 have their upper textures on the wrong side, but the HOM is visible only from the chainsaw platform before its walls have been lowered.

One end of the chaingun can clearly be seen through the low wall which obscures its platform (from the left edge of the curved staircase, or from the right side of the bridge if approaching from the chainsaw area).

The following actions can trigger the blockmap bug:


 * From the extreme western edge of the first room, firing into the central area (not along the blue gallery).
 * Firing along the blue gallery at a slight angle.
 * Attacking a Demon in the first section of the red key corridor.
 * Firing westward in the northern part of the large octagonal room.

Slime trails may be visible in the following locations (see screen shots below):


 * Just past the first door, looking toward the yellow key alcove.
 * Outside the red door, looking southeast.
 * At the T-intersection on the western edge of the first room, looking east.
 * Looking along the blue gallery from the west end.
 * Looking at the northern slime pool through the window in the first room.

Demo files

 * [[Media:e1m7secr.lmp|No monsters, 100% secrets walkthrough]] (file info)
 * [[Media:e1m7wik1.lmp|100% kills, items, and secrets on ITYTD]] (file info)
 * [[Media:e1m7wik2.lmp|100% kills, items, and secrets on HTNR]] (file info)
 * [[Media:e1m7wik3.lmp|100% kills, items, and secrets on HMP]] (file info)
 * [[Media:e1m7wik4.lmp|100% kills, items, and secrets on UV]] (file info)

Routes and tricks
Due to the large population of this level, even a straight speedrun requires the player to obtain a shotgun in the first room and use it regularly. When fast monsters are present, the deaf sergeant hiding around the left-hand corner may be killed by the Imp behind him, which is slightly faster than simply using one's pistol. The structure of the map allows few major route optimizations (it is simply a matter of reaching the next key, then the next locked door, and so forth), but secret #2 is demonstrably a shortcut on the way to the red door, especially as there may be rather a mob in the computer room by that time.

A small amount of time can be saved in the first room by skipping the green armor, then returning to it after picking up the blue key (thus bypassing the crowded passage near the windows). The fastest Compet-N demos make use of two key barrel frags: the right-hand barrel at the column trap (allowing you to round the curve to the inside), and the barrel through the window just beyond the blue door (clearing the way to the button), but not at the entrance to the octagonal room, as there are simply too many interposing monsters for a clear shot. Conversely, later congestion can be eased somewhat by holding one's fire as long as possible after entering the red key corridor, after picking up the blue key, and after passing through the blue door (in all three cases, sound-blocking linedefs no longer lie between you and various monsters). The level has been completed without the blue armor or the radiation suit, even in NM.

NM speed runs tend to follow the UV speed route, although some players prefer to enter the computer room initially from the west, to avoid being cornered by the fast Spectre. Similarly, after picking up the blue key, some players detour to the center of the first room to avoid the large crowd along the western edge. The rocket launcher is universally ignored, although the chaingun should be obtained as soon as possible to use on large crowds, especially near the exit. Attempting to outmaneuver fast Demons in the confined area near the red key is normally considered suicidal as well. The current record holder actually skipped the chaingun, but admits to a few lucky damage calculations at the end (a lucky barrel frag in the octagonal room, and a lucky respawn pattern in which the sergeants at the column trap did not return, also appear to have helped).

It has been shown that, with fast monsters, charging straight at the column trap is fairly likely to cause infighting, since the sergeants have trouble dealing with the height difference at first. On the way out of secret #3, many players pause briefly until the brown column stops rising, then cross the trigger line, so as not to have to waste even more time on the way back from the red key room by running past it and waiting for it to descend.

In categories requiring 100% kills, efficiency is greatly increased by the use of rockets, usually upon first approaching locked doors behind which the monsters are already active, through the windows on one's way to the soul sphere, and in the southern part of the large courtyard (if your aim is good, you can kill all six deaf sergeants with two shots). The fastest UV max runs also fire one or two at the column trap, into the dark window just beyond the blue door, and, for maximum efficiency and risk, at the trap in the octagonal room.

UV max players, once the column trap has been dealt with, are advised to proceed in the following order:


 * pick up the chaingun;
 * clear the chainsaw room;
 * clear the red key room and its trap (but not the other trap just triggered, as those monsters will make their way to the northwest corner of the computer room with everybody else);
 * get secrets #1 and #2, emerging near the red door.

In the first room, infighting can be rapidly encouraged by firing one bullet to wake everyone up, then circling to the west in a start-and-stop manner, thus shielding yourself with the Spectre (while avoiding its attacks). The chainsaw room is most quickly cleared with a timing pattern:


 * shoot the Demon once with your shotgun;
 * run forward to kill the southern sergeant;
 * spin right to kill the southwestern sergeant;
 * keep turning right to shoot the barrel to the north, which will often knock down both the Demon and the remaining sergeant.

When 100% secrets is required, most players do not consider the radiation suit a detour, because it can be picked up while waiting for secret #1 to open. Although the chainsaw is essentially irrelevant in any category save Tyson, you should still go all the way into secret #1 for the rockets (and the medikits, if need be).

When fast monsters are used, congestion near the entrance to secret #4 can be a problem. Some players open and close the western yellow door a few times to encourage infighting, then run through the blue gallery and approach from the east side. If you have enough rockets left, you can instead fire two or three into the trap nearest the blue key, ensuring that the monsters in the other trap will have wandered northward by the time you arrive. Fast monsters also incite some players to dive into the extreme southwestern corner of the red key passage, where only one Demon can approach at a time, and (for styles requiring 100% kills) to grab the invisibility before going anywhere near the sergeants at the south end of the courtyard.

UV -respawn runs differ from UV max runs by ignoring areas of low population density, namely the chainsaw room and the large courtyard. These are generally recouped by killing monsters twice in the first two rooms (proceeding from the blue key to the yellow door slowly, as in a max run), by firing rockets through the window into the final passageway before stepping onto the rising column, and perhaps by shooting barrels in the octagonal room after picking up the blue key. Most players kill a few sergeants through the windows before pressing the exit switch, just to be on the safe side. A small amount of time can also be saved by dodging Demons in the red key corridor, so as not to have to stand there holding down the trigger.

Modern Tyson recordings begin by picking up the chainsaw as soon as possible, then using it on absolutely everything save barrels and groups of sergeants (even to the extreme of circlestrafing around mixed crowds to cut down the sergeants first). Because the first two rooms must be re-entered anyway in order to reach the red door and the blue door, this does not actually require modification of the UV max route, although secret #3 can be skipped because the extra bullets are not needed. Barrel frags are still quite important, especially at the column trap (lunge forward first so that the leftmost troopers walk toward the barrel), in the dark switch room, in the chainsaw room, and in front of the trap in the octagonal room. Running straight to the yellow key also leaves a lot of monsters alive in the first room, so it is advisable to proceed slowly from the blue key to the blue door. Xit Vono introduced the idea of using the chainsaw on the sergeants near the invisibility, which is slightly slower, but saves time in the long run because it increases the infighting near the exit door. He later optimized this by shooting the deaf sergeants at the extreme southern end first. Such tactics also reduce the number of zombies who must be fought at close range near the exit switch, so a small amount of time can also be saved by not picking up the health in the rocket launcher area (which in any event should wait until your second or third trip through the computer room, thus allowing most of the zombies to find the lift and come to you).

A pacifist run can be completed using the UV speed route, with the blue armor a brief but essential detour, though some players believe that luck is the most important factor in reaching the exit, especially in the crowded areas beyond the blue door. On the walkway in front of the yellow key, the sergeant and Imp can be dodged at close range by cutting the corner over the ledge. There is just about enough space to pass humanoids in the narrow passages leading to the octagonal room, and to run past Demons on the way to the red key, but before picking up the red or blue key, feint backward to force all of the monsters toward one wall, thus decreasing your chance of becoming surrounded. At the red key lift, drawing the first Demon out into the octagonal room can help also.

Current records
The Compet-N records for the map are:

Inspiration and development
Early versions of this level appeared as E1M4 of Doom 0.4 and E1M4 of Doom 0.5.