Judging from the LP videos, they're actually quite far along, and have working worldgen, crafting, combat, building, etc.
A few details to glean from the LPs:
*Every item has mouseover stats and descriptions.
*Crafting simply examines the items you're holding and any nearby workbenches, then gives you a list of all the items you can build at that time.
*Building a 'back' wall in a building takes a lot of materials, but it prevents monster spawning.
*Because blocks are so small, you'll use a lot more for even simple structures. However, trees can yield dozens of logs and don't take long to chop (the whole tree comes down when destroyed) and each log turns into 4 walls, so the rate of return is much higher.
*Furniture is already in. :woop:
*Various characters will 'move in' to your world when conditions have been met, and you can choose where to organize them, shelter them, house them, etc. Merchants are one of the first to move in, and will arrive after some brief adventuring has netted you a required amount of coins, and you have a suitable walled off area to move him into.
*Zombies (and probably other mobs) will pound on your doors all night trying to get in.
*The moon has phases.
*When there's a Blood Moon, Zombies will actually be able to breach walls and kick in doors after enough time. Zombie siege!
*Slimes drop gel which is used to make torches.
*There are a lot of goddamn items in this game.