Speedrun Tricks

List of Left 4 Dead 2 speedrun tricks.

There are collected and described 48 tricks on this page. Some of them include a video example attached on their names to demonstrate how it looks in action. Category item Misc. also contains patched tricks, that no longer work in the newest game version.

The old list of tricks from 2015 can be found here for reference, including unlisted tricks.

Engine

Here is listed engine-related tricks, that available almost in all Source Engine games. Names and description of some popular tricks are taken from SourceRuns[wiki.sourceruns.org] website for convenience.

TRICK_NAME	DESCRIPTION
Bunnyhop	Movement technique, when player can permanently increase speed using strafing.
No Angle	One of the bunnyhop methods, that uses joystick inputs and allows player to strafe w/o keyboard and camera rotation. During the play, client may switch the movement to the joystick, by binding +strafe console input command. Next, all sideways move directions become infinite. This trick is actively in use on surf/bhop maps in CSS/CSGO games (some trick's info taken from this page).
Edgebug	Jump on the edge of the map to reduce or avoid taking damage from falling. In L4D2 player can perform this trick only after entering in IDLE mode or vomitjar boost – after this actions player specific flags has FL_ONGROUND bit, thus game cannot properly use m_flFallVelocity buffer (since believes, that player on the ground) and cannot give stored fall damage.
Ladderjumping	Jump on a ladder when player doesn't take any damage from falling.
Ladderspeeding	Climb the ladder quickly.

Boosts

TRICK_NAME	DESCRIPTION
GL Boost	Grenade Launcher boost in the opposite direction relating to the projectile.
Commonboost	Boosts with Common Infected. Using a shove (especially if zombie is running) will increase the base speed. Gives the boost easier at slope surface.
Throwable Boost	Throwable rainbow-like boost. It's possible to simultaneously boost several players at once; Using an IDLE with Pipe/Molly make it more efficient, by transferring all projectile's speed as it would be with Vomitjar.
Long Boost	Pipe/Molotov horizontal boost in the same direction where projectile thrown (this boost, unlike others, doesn't invert velocity vector).
Miniguntrick	Using minigun to boost.
Tank Boost	IDLE-related Tank punching boost with the basic velocity of 800.
Spitter Boost	Spit boost relating to the Spitter's projectile.
Hunter Boost	Boost relating to the Hunter's jump. Required the Deadstop before boost (MOUSE2 must be pressed in advance). Enough difficult boost to make it without scripts. It's recommended to guide Hunter's leap right in the player's legs.
Jockey Boost	Similar with Hunter boost, but less efficient.
Charger Boost	Jump on the top of the Charger when he does his main attack.
Ladder Boost	Boost speed is equal to the horizontal (2D) distance from the teleport point to the destination point. Boost working due to the type of teleport: stuck teleport. The speed of the boost tends to the maximum if the angle between the direction of the teleport (towards the player on the ladder) 90 degrees (the angle is perpendicular). You need to look only towards the ladder; in this way further the angle of your camera no longer affects the speed of the boost, even though look directly into the ladder. Boost works this way due to the fact that the player moves after teleport to the ladder (hold W button after stuck).
??? Boost	Mysterious ??? boost. Glitch represents the flight on the Spitter's projectile (more detailed explanation ).
Super Boost	Just a mix of various boosts (usually with very high speed), when using two or more other tricks (for example Throwable Boost + Commonboost (simultaneously explodes vomitjar and makes wanderers run near to the player to help him get more speed)).

Skips

Description of the time-saving tricks mostly during Finale holdout panic events. Some individual other maps' skips may be presented here as well.

TRICK_NAME	DESCRIPTION
Jesus Spot	Any spot where NPCs have no route to reach the players (due to the bad NAV connections), so it lets easier to survive. During holdout events it can save bunch of the time (preferred for RTA runs).
Cointoss	Works in patches before TLS update. This trick works only on c2m5 and was discovered there as a result of bad patches of the earlier game versions. We can skip the landing chopper animation on the left side of the rescue zone, if survivors stay within the trigger before 'finale_escape_start' event. It happens because trigger [ibb.co] change its state for a 0.1s to 'enabled', allowing players to enter the cutscene and complete the campaign faster (source page of this trick with more info). Note that, the trick is unpredictable as it we cannot exactly know where chopper will land (chance 50%), but can be easely scripted for TAS.
Stage TANK Skip	Skip the Tank stage on the finales of some maps. After trick is done, server console receives this [ibb.co] error message. Can happen at different situations: 1) In case survivors saved a non-finale Tank after TANK stage start (so finale's Tank won't appear); 2) And if survivors overlap all potential finale-area spawns – works randomly and seems on l4d1-finales only (effect increased relative how much survivors involved to observe).
Stage DELAY Skip	Works in patches before TLS update. We can skip entire DELAY stage (about 20 seconds in total) for l4d1-finales at Realism mode.
Instant Finale	Mainly, this thing is a bug of the VScript virtual machine that prevents all Squirrel scripts from loading (such like: crescendo, onslaught, silent Director, no threat, no bosses etc.) and of course including any *_finale.nut script as well. It may randomly happen on the dedicated server, probably because of the prolonged work (players join on the already broken, overplayed server). By the way, during TLS patches it was finally fixed [ibb.co] . So, what is the Instant Finale? It means that every finale stage (DELAY, PANIC and TANK) will be immediately skipped and rescue vehicle will appear in 5-10 seconds after pressing a radio. Unfortunately, there are no legal speedrun examples exist with using of this "trick", but you can see the simulated version , how might Instant Finale approximately look in speedruns. It turned so speedrunners are used to host the local server usually, where most likely no chance to meet the bug... that's why there's still no relatively stable way to perform it somehow. Apparently, for the proper finale skip implementation, the personal dedicated server is required (as well as an old game version, below 2.2.2.5), then it must be corrupted during testing and re-hosted again for the speedrun. The players have to be sure, that bug will happen shortly.

Teleporting

Abusing of the game code, that created to help the player/bot exit from the stuck situation on the map. Speedrunners in L4D2 use teleports to do various warps (for more information read the Warps section below).

TRICK_NAME	DESCRIPTION
Normal TP	Simple SurvivorBot teleport to the nearest player with 6.1 seconds teleportation timer. Usually this trick implemented outside the map, where there aren't NAV-connections to the player's position, and if following conditions are met: 1) The bot is a TP-ready bot (i.e. stood still longer than 4.7 seconds). 2) Players don't see the bot. 3) Distance between player and bot more, than 1500 units. 4) There is nobody next to the saferoom area.
Long TP ‎	Long SurvivorBot teleport with 16.1 seconds teleportation timer. To make this teleport, players should to keep eye contact with a TP-ready bot for all 16 seconds. A main feature of this teleport is that bots can teleport despite the fact that a player is looking, doing Long TP as rather stable and useful for some cases.
Omni TP	Omni SurvivorBot teleport works according to the simple teleport rules. Players can control this teleport and perform immediately at any time, by pressing IDLE (even in case if bots stand in playable NAV-area). Make sure that bot entered in IDLE mode 6 seconds ago and stood still near the human player at least 4.7 seconds for success.
Stuck TP	Teleport with a theoretical minimal 10.1 seconds teleportation timer (TODO: how to test this teleport?). Timer starts when the player is stuck in any solid (as a rule worldspawn ). Teleport will occur to the nearest survivor. Works only with a non-bot players. Player may also get stuck in a zombies, using a gascan; in the Tank, when he climbs somewhere; or in the displacement , by pressing a crouch button ( case #1 , case #2 , case #3 ).

Warps

Any action that takes you from one area of a game to another without traveling there.

This section can be combined with Teleporting because teleports are considered to be warps as well, but it still separated to prevent any confusions.

TRICK_NAME	DESCRIPTION
XClip‎	Simple IDLE-related cross clip warp, when player warp over wall and can reach nearest behind the wall locations or OOB area even. In case if player stuck in solid and performed IDLE (go_away_from_keyboard) or vice-versa take bot control (sb_takecontrol), engine might drop him in other place. For example, bot can stuck after teleportation to the player, who stand next to the wall with his back. Developers added a little shift back (10 units) at SurvivorBot teleportation in player's position to make this situation more realistic. Speedrunners prefer to use bot teleport for warp foremost. Also, player may use physics objects near the wall to make these warps.
DXC ‎	Double IDLE-related cross clip warp. Some warps can be completed only after getting more deeper stuck in the solid. In case of the failure after simple xclip warp, other survivor bot can still try to teleport to stuck player. The depth of the stuck in the solid of second player will be already about 20 units (xclip + xclip), thus warp can occur.
DDXC	Double IDLE-related defibrillator cross clip warp works similar like DXC warp, but with defibrillator. The reason of using of defibrillator is that because sometimes player can unstuck from solid after take bot control. To make player takeover bot and be inside the wall, he must be killed and respawned by defibrillator. After respawn, player already play as himself, so second warp can be done.
SXC ‎	Stuck cross clip warp performs after stuck teleportation to the hopping player who touches the ceiling.
Level Warp	After the changelevel, players' positions are saved relative to the info_landmark entity. Speedrunners abuse it, using instant reviving by the defibrillator (similar to fast healing/reviving/deploing in the saferoom) together with a stuck warp to reach the far places after the map transition. Also, non-player entities can be transmitted between maps and even other campaigns (shown in this example).

Misc.

TRICK_NAME	DESCRIPTION
AFK Tricks	In that video were collected and described the most popular IDLE-related tricks, that are frequently used in speedruns.
Immortality Glitch	Glitch occurs due to the fact that the player doesn't loaded into the game correctly. Such a player cannot interact with anything, only open doors, break windows and kill commons by stepping on them, and also becomes immortal.
Zombiejump	Jump on CI to reach inaccessible spots.
Commonladder	Allows to climb upright on several CIs at same the time, in places where infecteds' ladders are.
Climbing	Boost a player vertical to make him hang on the fence.
Superstrafing	Increasing of the strafe angle while bunnyhoping, when in the air player stretch from the crouching (i.e. has only FL_CLIENT bit). Superstrafing usually works w/o the crouch holding, when the player flies close to the edges , but doesn't touch them. So, after this, player's air accelerate increasing and we start to rotate mid-air more efficiently. Also works, if player came off from the ledge right on the GL (no jumps) or simple jumped on it with the additional 2D speed (approx more, than 300 velocity), thereby increases his strafe angle after the boost.
Tap Crouching	Movement technique, that allows player stretch from the crouching faster by single pressing crouch button. Game will force crouching, if player jump and land on an object, that still higher than player's full standing height.
Defibrillator Abuse	Use defibrillator respawns to skip the triggers.
Conversion Abuse	Specific manipulations in order to get needed item (usually defibrillator) for speedrun purposes. Explanation: game will try to convert items each 5s after 'round_start' event or after 'difficulty_changed' in case it was changed. Defib appeared in case we have B&W guy and other players have >= 50HP. We need to spawn close together 2 any 'slot5' items for defib. First convertation will always be to medkit, due to we have B&W guy with < 50HP. Defib will NOT appeared, if someone else has < 50HP, medkit spawned instead. For conversion, difficulty must be NOT expert. Also, flow distance between player and items must be < 2000 and player must AVOID eye contact with converted item (but player still can look towards items, if we have > 1000 flow distance).
Vote Kick Abuse	Abusing of the 'Call a Vote' system to kick the SurvivorBot, by using player's userid. Usage: callvote Kick user_id Originally, the trick is a console exploit and considering enough controversial because Developer Console abuse may go too far. However this trick is famous among OG players and actively used in Co-op, Survival and Versus game modes, therefore can be quite legal for someone.
GL Fast Kill	Works in patches before TLS update. IDLE-related granade launcher fast kill. Used to kill teammates quickly.
Stunbug	Jump in the radius of the explosion or stun-sphere (stuns from Boomer or Charger etc.) to avoid taking damage from falling.
Infinite Stumble	Works in earliest versions, like 2.0.0.0 etc. Very old and famous trick in L4D2, existed since the game release. Player should switch between primary and secondary weapons rapidly for a full duration of a stumble before actually stumbling without falling off.
Item Dupe	Creating an item's duplicates by pressing USE button simultaneously with other players. Not all items can be duped. Works only with *_spawn items?

[No name?]

м

[1337]

hehe boy

[シェイディ♑]

How it exactly works? And what reason is that trick doesn't work on 2.1.5.5?

[untilt]

Cool,will be attached soon

[Not Pinky]

What about "Ladder Boost" aka "Ladder Launch"? Also I don't know how useful this trick for speedrun, but if you add it to your list maybe someone find way to use it https://youtu.be/69zvDBIms0k (also I know this trick doesn't work on 2.1.5.5 version. Only in newest and older than 2.1.5.5 versions)