Portal was the first Valve-developed game to be added to the OS X-compatible list of games available on the launch of the Steam client for Mac on May 12, 2010, supporting Steam Play, in which players that had bought the game either on a Macintosh or Windows computer could also play it on the alternate system.
1 Eurasian Pleistocene megafauna became extinct in roughly same time period despite having a much longer time to adapt to hunting pressure by humans. 2  However, the extinction of the Eurasian megafauna can be viewed as a result of a different process than that of the American megafauna.
The PermianâTriassic extinction event is the most significant event for marine genera, with just over 50% (according to this source) failing to survive.here is evidence for between one to three distinct pulses, or phases, of extinction. There are several proposed mechanisms for the extinctions; the earlier phase was probably due to gradual environmental change, while the latter phase has been argued to be due to a catastrophic event.