Have you actually tried playing anything after doing that? If you want to actually play offline, you need to enable offline mode, run the game you want to play so it updates (even though when I tried it with TF2 it downloaded nothing, but still wouldn't play until you ran it first in online mode), and then it will be available in offline mode.
Regardless of difficulty, it's pretty ridiculous that you have to prepare for an Internet outage.
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Have you actually tried playing anything after doing that? If you want to actually play offline, you need to enable offline mode, run the game you want to play so it updates (even though when I tried it with TF2 it downloaded nothing, but still wouldn't play until you ran it first in online mode), and then it will be available in offline mode.
Regardless of difficulty, it's pretty ridiculous that you have to prepare for an Internet outage.