You know that first level of Mirror's Edge? I'm quite good at that. Pretty quick. Adequate. Such limited achievement at being fast in games is a small comfort when faced with this: a new world-record segmented speedrun of Half-Life. The speedrunning team of quadrazid, CRASH FORT, coolkid, pineapple, YaLTeR, Spider-Waffle and FELip have completely demolished Valve's 1998 FPS, beating the previous record by nine minutes. If you've got a spare 20 minutes (and 41 seconds), it's well worth a watch. Gordon's balletic flight through the halls of Black Mesa is almost mesmerising in its fluidity.
According to the team, the run took "almost four years of painstaking planning, theorycrafting and execution". It's a segmented run, which means the game's been divided into repeatable (and perfectible) chunks. In fact, the video's description reveals that over 317 segments were used, over 200 of which were under five seconds in length.
Additionally, the run makes heavy use of custom scripts. As the runner explain, "the most widely used scripts are jump spam, duck spam, 180º turn for gauss boost and precise use-key actions."
For comparison, the best single-segment run is 36:58, by Max 'coolkid' Lundberg, who was also part of the segmented team. You can see that slightly less acrobatic achievement over at Speed Demos Archive .