Woohoo today is the day of the survival single player test! Its not up yet and also you will have to have a purchased version of the game but here is some info posted by Notch on his blog.
I'm leaving for my dad's place for the weekend now, so no more updates on tumblr. I might still tweet, though.
As I've underestimated the amount of work needed for survival mode, it won't have everyting, but:
What is already done:
* Random mobs roaming the land
* Resource management (need to gather to be able to use)
* Falling damage, drowning damage, lava damage on both the player and the mobs
* Attacking causes damage to both players and mobs
* Very limited signs. Press H to spawn a sign with a fixed message.
* Anaglyph 3d mode
What will be done:
* Eating mushrooms regains health
* Death animations on monsters
* Pigs dropping meat on death. Eat meat for even more health
* Some kind of goal so you can compare how well you're doing with others, and so there's something to play for.
* Bow and arrow. You'll start with a bow in your inventory
* Better mob AI
What (almost certainly) WON'T be in that should be in, but I might add any of these if my monday or thursday coding sessions are extra productive, but that's not a promise:
* Crafting
* Good mob AI
* More mobs
* New block types
* Everything else
