A Reddit user has dug into Fallout 4's files and extracted information about the upcoming Survival difficulty - and it sounds like it significantly changes the game.

Come on Dogmeat, let's see what they've got.

We already knew about some of the game-changing features Fallout 4's Survival difficulty adds. Now we know a lot more.

Survival difficulty disables manual and quicksaving. To save you need to find a bed and sleep for at least an hour.

Combat is described as "more lethal" for everyone, so while you now deal more damage, you also take more damage.

Fast travel is disabled, so you have to physically travel to where you wish to go. This is a big deal for a game without any mode of in-game transportation. Happy jogging!

Ammo now carries a small amount of weight, which varies by caliber. The information warns that heavier items such as fusion cores and mini-nukes "can really drag you down". One for Fallout 4 encumbrance fans, then. There are fans of Fallout 4 encumbrance, right?

Enemies will no longer appear on your compass, and the distance locations of interest appear on your compass has been shortened.

On combat, Survival difficulty automatically grants the Adrenaline perk, which provides a bonus to your damage output. Great, right? Well, the only way to increase your rank of the Adrenaline perk is to get kills, so you have to get stuck in. Also of note: sleeping for more than an hour causes your Adrenaline rank to lower. Interesting risk / reward there.

Survival difficulty adds the "Wellness" feature. You have to stay hydrated, fed and rested to remain combat-ready. Letting yourself go can affect your health, hurt your SPECIAL stats, and add to your Fatigue. It can also lower your immunity and, eventually, deal physical damage to you.

Fatigue is like Radiation sickness but for Action Points rather than Hit Points. It shows up as red on your AP bar.

Sickness is caused by eating uncooked meat, drinking unpurified water, taking damage from disease-ridden sources such as ghouls and bugs, or using Chems. When you're affected by an illness a message will appear on-screen. Antibiotics, crafted at Chem Station or bought from doctors, heal sickness effects.

This content is hosted on an external platform, which will only display it if you accept targeting cookies. Please enable cookies to view. Manage cookie settings

The type of bed you sleep in determines the length of time you're able to stay asleep. A sleeping bag, for example, will save your game but will never allow for a full night's rest and its associated benefits.

Crippled limbs will no longer auto-heal after combat. You have to heal with a Stimpak to sort those out.

And get this: exceeding your carry weight reduces your Endurance and Agility stats and periodically damages your legs and health. Bethesda's doubling-down on encumbrance with this Survival difficulty, then.

On companions, they'll no longer automatically get back up if downed during combat. They return home if abandoned without being healed.

And finally, locations you've cleared now repopulate enemies and loot at a significantly slower rate. So farming will be a thing of the past.

Survival difficulty sounds fantastically challenging, and should breathe new life into Bethesda's post-apocalyptic role-playing game. Based on the leaked information, it's just the kind of proper hardcore mode Fallout 4's been crying out for.

There's no release date yet, but we suspect it won't be long before the free update is pushed out in beta form.