Free Metro 2033 codes

Saw this on PCSpecialist earlier and decided to share it with you lot too (don't think there's already a thread on this):
https://www.facebook.com/MetroVideoGame/app_395840630491782

OP:
https://www.pcspecialist.co.uk/forums/showthread.php?21572-Free-Metro-2033

Enjoy, you need a facebook account & have to like the page, that's it, no sharing the page or anything like that.