Making custom maps have a Challenge Mode
It's all in the title. I haven't found a way to pull it off. Any ideas?
My Work
[spoiler]Maps:
Revenge of the Angry Turrets
Capture the Cube [Co-op]
Capture the Cube 2 [Co-op]
TPWEGTH Sample Map
Aperture Aquatic Testing Center
Aperture Aquatic Testing Center 2
Aperture Time Testing Center
ML's Halloween Trick - 1000 downloads!
ML's Halloween Treat
ML's Combination - 1000 downloads!
ML's Jailbreak Labyrinth
ML's Tricky Teamwork [Co-op]
WIP:
"Capture the Cube 3"
Workshop Maps Link: http://steamcommunity.com/profiles/76561198008890579/myworkshopfiles/[/spoiler]
I'm sure there's at least some way to display the timer/portal counter, probably with some sort of script. Uploading results to the official leader boards wouldn't work, though.
Yeah, I wasn't counting on that. I feel that players would play the maps others have made a little more knowing there would be a little bit of a score competition in it.
My Work
[spoiler]Maps:
Revenge of the Angry Turrets
Capture the Cube [Co-op]
Capture the Cube 2 [Co-op]
TPWEGTH Sample Map
Aperture Aquatic Testing Center
Aperture Aquatic Testing Center 2
Aperture Time Testing Center
ML's Halloween Trick - 1000 downloads!
ML's Halloween Treat
ML's Combination - 1000 downloads!
ML's Jailbreak Labyrinth
ML's Tricky Teamwork [Co-op]
WIP:
"Capture the Cube 3"
Workshop Maps Link: http://steamcommunity.com/profiles/76561198008890579/myworkshopfiles/[/spoiler]
There's a map list of maps that have challenge modes somewhere in the Portal 2 directory. You would need to do this with a .vpk (which don't work right now) and copy the challenge mode map list .txt file into the appropriate place in your .vpk and edit it so it has your map name.
[spoiler][SP] Alternate[/spoiler]
one thing you could do *WARNING: BAD IDEA (did I say bad idea?! I mean HORRIBLE IDEA!)* is build your level in a big box, and fill that box with a func_portal_detector... add a math counter and you can count the number of portals!
Then I'm sure you can use a logic_timer to get some sort of timer too...
Best idea is just to stick withcordwann's idea 
lol or rather than a huge box just fill the inside of the map....it could work.
I think in terms of boolean variables. Generally, it makes things easier.
Yes, the point is that the all the white surfaces are covered
But I still believe it is a horrible idea
MEGABUMP TIME o/
I've been trying to get this to work (personally, not for distribution inside a map), just for kicks. The pertinent file is under the dlc1 folder and it's challenge_maplist.txt by the way.
Adding an entry to the list with the name of an official SP map - actually works! there's even the correct name of the map listed! and even working leaderboards!!! No challenge mode flags though, fortunately the timer stops when the map would normally transition. Plenty of speedrunners do this to compare times on non-challenge maps like Portal Carousel or Finale 1.
I tried it with a custom map - dug up the path to the .bsp in my maps/workshop/(numbers) folder and pasted it into the challenge map list, formatted it like the others. It adds an invisible entry to the challenge mode map list, but it doesn't seem to work if I hunt it down and click on it, giving me -> this lovely error. I guess it's just not possible then. Bummer.
Then I'm sure you can use a logic_timer to get some sort of timer too...
Best idea is just to stick withcordwann's idea
Or you could just create a couple prop_portals, and use the output OnPlacedSuccessfully << <Mathcountername> << add << 1.