Speedruns are often reliant on the most random, funnily obscure quirks in any given game. You don't need to look further than the recent Half-Life 2 20th anniversary update for proof, as Valve added a fix to the two-decade-old game that accidentally broke a small speedrunning strategy, and it's now had to fix its 'fix.'
Valve could have probably messed with speedrunners by rejigging any square inch of Half-Life 2, but this time it added an invisible wall to a giant sewer pipe in the Route Kanal section of the game, which you can see in the playthrough video below. As explained by Rock Paper Shotgun, Valve seemingly always wanted the pipe to be blocked up until the player completed a puzzle, flooded the room, and was able to swim through it.
But SourceRuns explains that the 'player clip' was previously only present in the Xbox 360 version of the game, oddly, so PC speedrunners were free to skip the puzzle using unconventional and sometimes glitchy means, like defying gravity with a cursed barrel to lift yourself into the pipe. Some players bunny hop across the level and flood the area sooner instead, so the new invisible blockage might not have affected every player.
Regardless, the rest of Valve's hefty update has locked some speedrunners out of various other strategies, big and small, meaning it's probably best to play Half-Life 2 on an older build if you're planning to whizz through it as fast as possible. For now, as of earlier this week, Valve has at least "removed collision from an underwater tube that speed runners enjoy," as it writes in its latest patch notes.
