Portal under Linux came out

First released in 2007, the sequel to the 2011 iconic Portal game is fully ported to Linux. This is stated on the official forum steam .

Install Portal (of course, if you already have Steam ).

If you already have a purchased version of the game under Windows, you can install it for free under Linux. If not, it will cost you about $ 9.99 / £ 6.99
')