INSIDE is the follow-up to LIMBO by Playdead. The Steam key is available from Green Man Gaming for £8.99 if you login (getting the VIP discount to £9.99) and then use the 10% off voucher WINTER10 (thanks to jwsg in the previous thread). It's part of their Winter Sale
and includes a free mystery game).
There's an INSIDE demo
on Steam if you want to try it out.
"Hunted and alone, a boy finds himself drawn into the center of a dark project."
87% Metacritic: http://www.metacritic.com/game/pc/inside