Contrary to all the answers on here, it is in fact possible to reset your progress in co-op. Make sure you are the host (you invited your friend, rather than you were invited by your friend). Start a co-op game. Make sure you are in the hub when doing this.
Warning: This applies to both players. Make sure the other player is fine with you doing this.
Unfortunately, this doesn't work with ss_map
. You have to be in a session with another player, and this will set both players' progress.
Enable the developer console in the options, then press ~ to open it. If you are having trouble, see this question. Then, enter the following command in the console:
mp_mark_all_maps_incomplete
You might see a weird message about DLC, but the command will have no other visible effect. Now, enter this command:
changelevel mp_coop_lobby_2
This will reload the lobby, and your progress will be reset at zero.
You can use this command to change your progress manually:
mp_mark_course_complete <course>
Whereas the number is the number of the course you want to unlock (have finished), minus 1. So to unlock course 1, use mp_mark_course_complete 0
, to unlock 2, mp_mark_course_complete 1
, and so on. This means that mp_mark_course_complete 0
unlocks course 1 fully, and will then open 2.
There is also mp_mark_all_maps_complete
if you want to get Professor Portal.
Thanks to fail badp♦ for allowing me to waste his time.
Best Answer
In Valve games you are able to record demos that capture every tick of information, so players will record a full set of demos then put them into a program that counts the number of ticks. In Portal 2 (dunno about Portal) the tick rate is 60 Hz, so the time is ticks/60 (which is why any times you see down to the millisecond will be multiples of 1/60).
Exceptions are made at the start and end of a run for when the player actually gets control, usually deemed to be when the crosshair appears/disappears. Runners will open up the demos, step through them frame-by-frame watching the crosshair, then subtract that many ticks.
More generally as to how speed runs are "officially" timed, the most "official" (notice the quotes) body I know for speed-runs would be the Speed Demos Archive, who maintain a decent amount of runs across various platforms. They have an FAQ about how to time runs, but some communities can be strong enough to add game- or engine-specific exceptions to their general guidelines.