- How to start the map editor in Portal 2 and play it:
1.Go to Portal 2 on Steam and right click on the name,
and then a menu will come up.
2. Press SET LAUNCH OPTIONS...
3. Enter -console
4. Start Portal 2 and then you will notice there's a console
on the main menu.
5. Enter : map po2_edit01 for the normal map editor.
Enter : map po2_ug_edit01 for the map editor with the underground Aperture
science textures and things.
- How to play coop on the map editor:
1.Invite a person to coop.
2.When the loading screen is complete, enter: changelevel mp_coop_po2_edit01
in the console.
But only the hoster of the server can build((Atlas)), the other can watch and play.
Do remember to save, if you die the map doesn't get saved.