MAC Game not starting

[dramsenik]

HI,
I bought this game and under specs it's written Snow Leopard 10.6.8 ou plus récent
Processeur : Série Intel Core i
Mémoire vive : 4 Go de RAM

I bought it, downloaded and now it tells me that this game is not supported on my plateform, it doesn't start. Which is by the way an iMac with just the same specs.

Any insight about this ?

I have two other steam installed games who runs fine, portal and portal 2.

Thanks for any help.