E2M4: Deimos Lab (Doom)

E2M4: Deimos Lab is the fourth map of The Shores of Hell in Doom. It was designed by Tom Hall and Sandy Petersen and uses the music track "They're Going To Get You". The par time is 2:00.

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.

Overview
E2M4 is arguably more difficult than some of the levels which follow it. The open layout distinguishes it from most other Doom maps, which are largely composed of rooms closed off with doorways and connected by hallways. Consequently, for example, fighting monsters in the first room normally alerts imps as far away as the opposite side of the level (due to the gunfire sounds from the player), who begin to close on your position.

This level also features several large enemies, groups of monsters released by triggering traps, and several crushing ceilings some of which are cleverly disguised. The player can lure monsters under the moving ceilings to conserve ammo.

Essentials
Walk forward and enter the teleporter (A). Take the first left and continue west across two rivers of nukage. At the end of the hallway, turn north, then west, then south and go through a big metal door (B) to find a lift. Press the button to lower the lift, and ride up to the blue keycard.

Return through the big metal door heading north. When the hallway turns right, follow it but then quickly turn left. Continue north to come to the blue door (C). Go through to see the yellow keycard. Grab it quickly, as the ceiling is a crusher.

Go through the nearby yellow door and turn left. Follow the circular hallway and take the first right, going down a red lift (D). Go around this lower hallway in either direction until you come to a green switch on the inner wall. Click the green switch to raise stairs, and go up. At the landing, there is another green switch. Click and go up; repeat at the second landing.

In the room at the top there is a raised square platform (E). Walk onto the platform to open a tall door (F) back at the bottom of the stairs. Descend the three staircases, go through the doorway you just opened, and teleport.

The hallway ahead features a scrolling graphic behind bars. Walk down the hallway to see the exit door, inaccessible across a pool of blood. Jump into the blood and run to the small alcove (G) just to the lower left of the exit door. Click the skull switch on the south wall of the small alcove to raise a bridge across the blood. Take the teleporter behind you in the north of the small alcove.

You are back to where you last teleported from. Walk out of the teleporter and then back into it to teleport again to the hallway with the scrolling graphic behind bars. Walk down the hallway and across the now-raised bridge to the exit door.

Other points of interest
After you cross the two rivers of nukage, take the first doorway to the right. On your left, you will soon see a lighted computer room containing medikits, a shell box, and a green armor. As you step into this room, however, the floor of the hallway behind you will rise (H), trapping you inside until you hit the switch at the opposite end (I). Not only is this guarded by a group of monsters, but the large central structure is a crusher, activated by walking under it at the east side. Note that you can permanently block yourself from entering this area and secret #5 below: by moving very slowly, you can raise the floor without quite entering the computer room, which permits you to return southward and fall down into the blue corridor with no way to get back up.

On the platform where you got the blue key, click the switch on the south wall to lower the half-high wall to the east. Follow the walkway, through a pair of crushers, until you see a crooked, narrow bridge (J). Carefully cross the bridge to obtain several ammo pickups and a radiation suit. (When first activated, these two crushers can easily be traversed together by running straight ahead. If they have crushed someone already, however, they tend to get out of sync and require more caution.)  To avoid encountering the crushers again, you can jump off the bridge to the north and turn right down the nukage passage (K), which returns you to the start area.

If you turn left at the blue door instead of proceeding straight through, you will come to an alcove with a backpack (L). On Hurt me plenty and higher, a cacodemon is also present.

Note that the yellow door is a single-use linedef on the front (west) side: if a player or monster subsequently activates it from the back side, it cannot be reopened from the front even with the key. This may well confine you to the earlier regions of the map, making the exit inaccessible.

After going through the yellow door, turn left and follow the circular hallway (past the red lift on the right) to a doorway on the left, revealing some curved stairs. Go down the stairs into a room (M) with a short wall on your left, overlooking a pool of lava, and five metal doors on your right. The central door conceals a shell box and a medikit; as you approach these, the two adjacent doors will open, releasing several monsters.

In the tall room with the three rising staircases, there are two small rooms on the north wall, adjacent to the red lift. As you leave the lift, watch out for projectile attacks from the eight imps (I'm too young to die and Hey, not too rough) or twelve imps (HMP) or eight imps and two barons of hell (Ultra-Violence and Nightmare!) inside. Stepping on the two lowest stairs will raise the floors of these rooms slightly (N, O) so the monsters can enter the main room; this occurs even if you haven't clicked the green switch yet. The small room on the left contains a button which lowers the red lift.

Secrets

 * 1) At the start, there is a slightly off-color wall to the right, opposite a blinking light. Go through this hidden door to find a shotgun, a shell box, a bullet box, and a medikit.  Note that you do not have to walk all the way to the shotgun to get credit for the secret (sector 188).
 * 2) At the far end of the large hall you teleport into from the start, there is a square lift. Go up and around the short hallway to find green armor and a computer map behind an array of tall pillars (P). Walk very close to the short red pillar to the east of the tall pillars (it has a skull on top). The tall pillars will then lower, along with the north wall behind them which releases some monsters. To register the secret, you must walk into the small room to the north (sector 16), which also holds a supply of ammo.
 * 3) As you approach the two rivers of nukage, instead of going straight across, turn left and follow the oval structure around to the right; this route will trigger a large door to the north (Q).  Continue around the circular nukage river clockwise, and go through the new door to find demons, spectres, a soul sphere, and a radiation suit.  (To reduce damage, go to the blue key first and collect the radiation suit in the area behind it, as described above.) (sector 10)
 * 4) The crooked, narrow bridge beyond the blue key spans a rectangular nukage pool; in the southwest corner of this nukage pool is a platform (R) with a berserk pack (sector 165).  You can also reach this platform by going southeast from the circular nukage river, through a blue-floored passage.
 * 5) After you cross the two rivers of nukage, take the first doorway to the right. A door ahead on your right will close (S). Shoot it with an impact weapon to reopen it. Go through to find a blur artifact and a chaingun. (sector 120)
 * 6) In the room with the pool of lava and five metal doors, go through the rightmost door. There is a compartment across a nukage pool with some barrels; explode them from a distance. At the back of this compartment is blue armor. (sector 107)
 * 7) In the room with the pool of lava and five metal doors, the leftmost door will open as you approach the nukage pool in front of secret #6.  Go through the leftmost door and follow the hallway around to a room with armor bonuses, health bonuses, and a few other items (sector 53).  As you enter this room, a section of the floor will rise to block the doorway (T), possibly pinning you to the ceiling, so run to the far wall immediately.  A door on the east side of the room, indicated by a green texture, allows you to get back to the hallway.  Note that the trigger for the leftmost metal door only works once, so if the door is subsequently closed from the back side, you can only reach this area via the lava pool (see secret #8 below).
 * 8) In the room with the pool of lava and five metal doors, hop over the short wall at the west end to find a platform with two medikits (sector 36).  To escape the pool, cross to the extreme eastern end and push the wall to raise a secret door (U).  This leads to the hallway in front of secret #7.
 * 9) After going through the yellow door, turn left and follow the circular hallway past the lift on the right and the doorway on the left. In the easternmost part of the hallway, the wall separates slightly from the floor. Drop down into the gap and push the wall to raise a secret door (V). Inside, find a plasma rifle (sector 19) and a teleporter to the raised square platform at the center of the three rising staircases.
 * 10) After you get close enough to the exit door to touch it, turn around. Another section of bridge will rise, enabling access to a soul sphere (sector 182).  Note that if you fall into the blood between the two bridges after both are raised, you cannot get out.

Bugs
Two "hanging torso" decorations (Things 202 and 204) have no flags set for any of the difficulty classes, so they do not actually appear in the level.

The north edge of the exit bridge (linedefs 934, 935, and 936) is tagged to the bridge (tag 16), even though the linedefs have no associated actions.

Sidedef 667 is missing its upper texture. This causes the ceiling of the lava room to bleed into the ceiling of the eastern platform (as seen from the back passage), which is clearly visible as a distortion of perspective.

Linedef 865 has its lower texture on the wrong side. This creates a slight asymmetry in the floor of the doorframe (sector 149), which has a "step" texture on one edge but apparently overlapping CEIL4_2 textures on the other.

Sidedef 1363 is missing its upper texture. The grid texture on the underside of the door (FLAT20) underscores the resulting rendering anomaly, as the grid appears to roll behind the ceiling of the passage (sector 55).

Linedef 1071 has its upper texture on the wrong side. This is virtually impossible to detect during normal play, because the upper corner of sidedef 1379 cannot be seen after the player has fallen down into secret #9.

Slime trails can be seen at most inner corners of the circular marble hallway; a trail may also appear as one returns to the exit door from secret #10. (See screenshots below.)

The blockmap bug may be triggered by firing eastward down the long blue corridor.

There are 12 known anomalies in this level's REJECT table.

Routes and tricks
Use the teleporter in secret #9 to avoid having to raise the three flights of stairs to the top-center of the circular structure.

When you click the skull switch to raise the bridge to the exit door, run quickly out to get on the bridge as it rises. This avoids having to re-teleport your way back.

In secret #5, if you run quickly enough, you can get through the door before it closes too far.

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

Inspiration and development
An early version of this level appeared as E1M13 of Doom 0.5, and may also be based on E1M10 of Doom 0.4.

This level was used to record the built-in demo in the very first shareware release of Doom.

Trivia
In single-player mode, this map contains 11 rockets (22 on I'm too young to die and Nightmare!) but no rocket launcher.