The 20th anniversary of Half-Life 2 saw Valve release for the PC gaming hall-of-famer (as well as an excellent two hour documentary). It integrated Episodes 1 and 2 with the base game (so you can now play through the entire experience seamlessly), added a new commentary track from the old gang, and for the coup de grace every location was given a glow-up: "Every map in Half-Life 2 has been looked over by Valve level designers to fix longstanding bugs, restore content and features lost to time, and improve the quality of a few things like lightmap resolution and fog."

Lovely! Except perhaps if you're a Half-Life 2 speedrunner, one of those freewheeling souls who's long ago stopped seeing the G-Man and looks at City 17 like the Matrix, pinballing the Freeman from checkpoint to checkpoint on Valve's hidden flippers. It turns out that, when improving everything, Valve's current designers added an invisible wall to a large sewer pipe. And speedrunners promptly started slamming right into it.

The map in question is Route Kanal or "d1_canals_03" and features a puzzle where the player has to turn a valve and flood the pipe in question in order to pass through. The upper section of the pipe is supposed to have an invisible wall to stop the player getting through before they've solved the puzzle but, for whatever reason, this has only ever been present in the Xbox 360 version of the game, and thus taking advantage of the missing wall (by glitching up the surface with physics objects rather than adding water) is a regular part of PC speedruns.

The Sourceruns wiki keeps detailed notes on the differences between various versions of Half-Life 2 and now has [[link]] a section devoted to the 20th anniversary update with various grumbles. Here it notes that "the pipe near the end of the level has been blocked off by a invisible brush which was previously only present in the Xbox 360 version of the game. The brush disappears once the player solves the puzzle in the intended way."

And what use is that to a speedrunner? Someone at Valve clearly noticed the disquiet because, a few days later, an update for Half-Life 2 reverted this fix with a direct nod to the reason why: "Removed collision from an underwater tube that speed runners enjoy."

The weirdest thing about this is that Valve's original fix was legit. It seems obvious in the context of the 360 version that this invisible wall should've been in the PC version of the game, and the fact it wasn't until now was an oversight on Valve's part. But I suppose the unforeseen consequences were judged to have merit in their own right.

This is far from the only speedrunning strat that the anniversary update has broken. Pity the poor rocket scientists who specialise in "d1_canals_11", because now "the skybox celling of the map has been substantially moved up, breaking old setups for launching over it." Other maps feature new invisible walls or adjusted collision points, and at points the speedrunners get straight-up stroppy about it: On "d2_prison_01" we find that "Every clip brush on the map, except for those on ladders had been removed, presumably by mistake."

There are, however, a few consolation prizes. Witness the delight of changes to "d3_c17_05" where "the door which the player is meant to use to enter a building has been made into a hole instead and significantly widened, making being fast a lot easier. Additionally, the floor texture in the apartments was changed from concrete to normal floor tiles. Makes sense!"

Half-Life 2 is not unusual among popular speedrunning games in having a community that splits over which exact version of the title is being used. The most popular era for Half-Life 2 seems to be the versions that existed just over a decade ago.

"We do primarily use older builds, most often ones from 2012-2013, especially at the top level," speedrunner "Peng", a HL2 world record holder, . "But at least I do find it unfortunate that we're missing out on some of the new changes, as some actually benefit speedrunners..."

Peng says changes to the "Item Save Glitch" means the anniversary build is unlikely to prove popular with speedrunners, as this allows users to skip entire sections of the game and save big time by glitching through certain walls. Though he does grant, with casual brutality, that Valve's fix-reversal will make it "viable for beginners" again.

The main thing with the anniversary update for us mere mortals is the wealth of Half-Life 2 material that came alongside it. Valve 's documentary serves as both of a making of the [[link]] game and a time capsule of an era where Valve wasn't yet Valve: , Testers were [[link]] going stir-crazy and , and for the first time we get some real insight into what went on .