Half Life 2 is encrytped- you need online access to register the game and have the installed files decrypted (takes an hour or so). Once this is done you have access to a program called "Steam" that you have to use as a platform to launch HL2. It basically stops piracy and adds instant access to HL2 and CSS all at once. You can enable an offline mode that means you dont have to sign into steam to get it to work but if you have broadband there is not point in it really. So yes, you do need online access and yes you dont have to sign in every time but no you cant save the files as it is just the decrypted version of the files plus extra from the CD. phew.