List of bugs used as features

[Kresjah]

Hi there!

I am currently working on a project which involves documenting all bugs in vanilla Doom (all versions) are/can be used as features in a map/wad. This list will help me determine what compatibility issues can arise when loading wads depending on these bugs in source ports which fix these bugs.

Please post bugs in the following manner:
Bug "name" ;; Doom versions containing this bug ;; short bug description or link to a page that describes the bug ;; A link to a wad available on the net containing this bug used as a feature OR name a map in the Ultimate Doom/Doom II/Final Doom games that uses this bug intentionally IF this bug has been used as a feature.

Please don't post bugs that seemingly can't be used as a feature.

Example:
Voodoo doll ;; All ;; Multiple player things will create a dummy object which acts as a voodoo doll for the player. http://doom.wikia.com/wiki/Voodoo_doll ;; TNT: Evilution Map 30

Do not post bugs from source ports (e.g. Legacy, Boom, Doomsday). Bugs posted should be from vanilla Doom.

Thanks for all your help!

[Grazza]

Nice idea for a topic. There are lots and lots, and making a comprehensive list is certainly a major undertaking, especially if you intend to record who first noticed and exploited the idea (this would take some resarch in some cases).

Notes:
* I have not given links to wads - you can find them using a search in the idgames database.
* I haven't always said "not used intentionally" in all cases where that is doubtless true for early examples - but all these could be used intentionally and many have been in more recent pwads as knowledgeable authors have taken them into account when making their maps.
* Some of these aren't bugs really, but are things that can be used in unintended ways, and have in some cases been changed significantly in some ports.

Here are a few (actually quite a few more than I had intended when I started to write this post, but still not comprehensive):

straferunning to skip linedefs ;; all ;; as running and strafing at the same time increases the player's speed, this means that he can sometimes avoid triggeting a linedef by running across it with sufficient speed

straferunning to cross gaps ;; all ;; the player can cross larger gaps than he can with normal running ;; e1m4, e4m3, Doom2 map03, and many others; Hell Revealed (hr) may have been one of the earlier pwads to contain some maps where straferunning is necessary

rocket jumps ;; all ;; the rocket blast gives the player a large speed boost, which can be used to cross gaps, skip linedefs or help with grabs (see below) ;; lots of examples, but one presumes e3m6 was deliberate (though more or less obsoleted by a switch trick)

voodoo doll ;; all ;; for picking up items on the player's behalf (moved by explosion or raising floor - no need for Boom's conveyor belts) ;; Plutonia map28

voodoo doll ;; all ;; for killing the player by telefrag ;; Evilution map30

voodoo doll ;; all ;; for ending the level by telefrag while in a damage/level end sector ;; can't think of wads where it has been used, but it has certainly been discussed

voodoo doll ;; all ;; for telefragging monsters ;; cydreams maps 31 and 32; ksutra map24; heroes e4m8 (killing spiders to trigger tag 666 in that case)

voodoo doll ;; all ;; triggering an action by crossing a linedef ;; ksutra map24 (exit linedef in that case); Eternal map26 and surely others

voodoo doll ;; all ;; for turning the player into a zombie ;; not sure if any use this deliberately, but it can be used as a speedrunning trick, since monsters that aren't already awake are not awaken by seeing a zombie player

glide through 32-unit gaps (asymmetrical) ;; all ;; shortcut - don't know if it is a bug that you can get through or a bug that it is difficult to get through, but probably the former ;; Doom2 map16, map22 and some others; many in pwads - generally not deliberately allowed, though some in recent demo-friendly pwads are intentionally allowed speedrunning tricks

glide through 32-unit gaps (flat-faced) ;; all ;; shortcut - requires low movement speed ;; Doom e4m4; Doom2 map19; Evilution map17; Plutonia map21, and some others; many in pwads - generally not deliberately allowed, especially since it has only recently been discovered

reduction of player's height upon death ;; all ;; this allows death slides when there is a gap under bars near an exit ;; plutonia has several examples, including map17, map31; many in icarus; scythe map11 ;; probably not deliberately allowed in the case of the iwad maps and non-recent pwads at least

dead players can exit levels ;; all ;; not a bug as such, but some ports remove it; obviously this is necessary for death slides to be of any use, or in cases where a voodoo doll exits the map after the player's death

archvile jump ;; all except Doom/Ult. Doom ;; arch-vile blast gives the player a height boost (and sometimes a speed boost) that can be used as a shortcut or to reach otherwise inaccessible areas ;; Doom2 map14 (some nice shortcuts, possibly not intended); many pwads have this as a deliberate feature - icarus map25 is an early example. Can be combined with a death slide (examples of that: ksutra map13, eternal map04)

wallrunning ;; all ;; player gets a speed boost (roughly double) by running south-to-north along a wall aligned in this direction ;; for examples, see any map with such a wall

thing running ;; all ;; player gains speed by running west-to-east along a row of things aligned in this direction ;; Doom2 map23 (probably not intended)

thing glide ;; all ;; when blocked by but still running up against a thing, the player preserves his momentum, so that when the thing is removed or the player slips off it, he moves at a little over full normal speed ;; e2m7, Doom2 map05

thing wobble ;; all ;; when blocked by but still running up against a thing, the engine seems to miscalculate the player's position, so he can sometime skip a linedef in this way (not 100% sure of this - presumably related to the thing glide) ;; tvr map10 (not intended, I'm sure)

grabs ;; all ;; a player can "grab" objects that are meant to be out of his reach (or the other side of a wall) by using sufficient speed or a "wobble" against a two-sided linedef (I presume) ;; e4m1 (red key grab); e2m9 (keys) Doom2 map16 (SSG grab) and others

switch from below/above ;; all ;; no height check for pressing switches ;; e2m2 and many other examples, and can be combined with something akin to a grab to press switches that are "too far" from the player's position

bars glide ;; all ;; when a two-sided impassable lindef meets a linedef at something other than a right-angle, it is sometimes possible for the player to get through that line ;; e1m3, Doom2 map10, Plutonia map07, extremal e1m7 and some others

monsters that can kill themselves ;; all except Doom/Ult. Doom ;; both pain elementals and arch-viles can damage themselves - the arch-vile with its own splash damage and the pain elemental because it can start infighting with its own lost souls ;; any maps with these monsters

levitation ;; all ;; there is a miscalculation in the transition from solid ground to air, meaning the player doesn't start to drop as quickly as he should. This helps with jumps in e1m4 and e4m3, and is used most spectacularly in Doom2 map07 - that also depends on the player's exact position at the gametic when he takes off

linedef crossing thanks to spechits overflow ;; a spechits overflow can result in a player crossing a linedef that he wouldn't otherwise be able to ;; strain map07 is the only example I know of that hasn't been specially constructed - it is the way the player is supposed to exit the map but I doubt the creators realized what they had done

stairbuilding can crush monsters ;; all ;; a rising step can have a similar effect to a crushing ceiling ;; any map with rising steps and a low enough ceiling above them relative to the height of the monsters that can be on them - extremal e2m7 features a crushable cyberdemon

OK, I hope this is a useful start.

You'll also find this page (http://www.doom2.net/~compet-n/index.cgi?action=nostalg) useful, though it hasn't been updated for some years and only deals with tricks on the iwad maps.

And this (http://www.classicdoom.com/odddemos.htm) on Ledmeister's site, though some of those are just quirks, and have no obvious application.

[Grazza]

The best known such quirk is undoubtedly the "arch-vile bug". I hadn't included this in my earlier post as I didn't have to hand a list of maps that deliberately use it.

arch-vile bug/"ghosts" ;; all except Doom and Ult. Doom;; when a monster has been crushed and left a resurrectable corpse, an arch-vile will resurrect it as a "ghost" monster (height = radius = 0) ;; no deliberate use in the iwads, but they can occur in most maps with an arch-vile; used deliberately in the following pwads (in rough chronological order, earliest first): gather2 map05, wtrfront, archie, icarus map24, hell2pay map14, 6pack map02, seej, eternal map25, hr map26, requiem map23, av map19, and surely others. Again, Ledmeister provides some useful information (http://www.classicdoom.com/ghostfaq.htm), including such things as a demo of a ghost pain elemental being created.