It seems that Valve has made Portal free on Steam. Until May 24th. Also on Macs.
The site's barely up and Steam itself doesn't seem to be able to connect to servers. Too busy
I would assume if they port a game to MAC, they would do what most other companies do, change the controls, otherwise all PC gamers would have to use controllers, and we certainly don't.
You can also get at 2-button mouse for your mac w/out too much trouble. Some even ship with two-button mice, since the puck has gone the way of the dodo bird...
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