Specimen Zero
Survive in the unfriendliest conditions that you could even imagine. Specimen Zero will put you in the middle of nowhere, giving you nothing except for the anxiety and dismay. What you will do depends only on you. Try to explore the surroundings and find something useful or give up and meet your death.
In the abandoned rooms of multiple locations, you will face many sophisticated puzzles. Find a way to overcome them or return to the already searched places. There are always some hints hidden, so you need to be incredibly attentive if you want to uncover all the secrets.
Although, you are not necessarily defenceless. Look for the weapon and this may save your life. But remember that ammo is not limitless and eventually you will need to replace your weapon with something else.