It's currently in the Alpha version, but it will enter the Beta version soon!
The game is about you (uh...). You appear in a magical world for no reason (there's no storyline at all, so you just appear there). You can cut some wood and dig around, so you get rough wood/stumps and dirt. Then you can build your first home. Well, home... Just be sure there's no larger entrance than 1 block when it gets night, because then the enemies (spiders, skeletons, zombies and creepers, aka 'exploding penises' (sounds like something for Niche

? Well, you will get why 'Seananners' calls them like that when you see them

"...)) appear. They aren't scary at all, since they're all boxy. The sounds do actually sometimes sound creepy, but w/e.
When you open your inventory, there are is a square, divided in 4 squares, in the upper-right corner. There you can place the rough wood / stumps you found, so you can make some regular wood / planks. When you fill all the four squares with regular wood, you can create a crafting-spot. Move it to one of the short-keys below and select it with 1 up until 9 or the Mouse Wheel, press the Right Mouse Button when the crafting-spot is selected to place it and right-click it again to use it. Now you have 3x3 squares and you can make a door by filling them with this:
W W X
W W X
W W X
W = Wood (Regular Wood / Planks)
X = Nothing
Some other useful tools:
Stick (V):
X X X
W X X
W X X
______________________________________
Axe (for faster wood cutting):
W W X
W V X
X V X
______________________________________
Pick-Axe (for mining):
W W W
X V X
X V X
______________________________________
Shovel (for faster digging):
X W X
X V X
X V X
______________________________________
Torch (makes sure monsters don't spawn in your house and lights your house up):
X X X
X C X
X V X
C = Coal (Found in deep caves and sometimes on the surface), looks like Stone, but with dark places on it)
______________________________________
Furnace (for heating things):
S S S
S X S
S S S
S = Stone
Place the thing you want to heat in the upper square and some burnable things, like Wood or Coal, in the lower square.
You can also replace the wood in the tools with Stone or Iron (I), which is found in deep caves and looks like stone with orange/pink places. Before you can use Iron, you first have to heat it.
If you want to play this awesome game, I suggest you watch 'Seannaners'' tutorials. But please note that the first few tutorials are in the previous version of the game, where there aren't any biomes yet and monster's aren't more resistant to light the lower you get.
You can still play the game offline right now without buying an account, but I'm not sure if this will still be the case in the Beta (I guess it won't be). Also, I find multiplayer way more fun than singleplayer (find a nice server or set one up yourself (maybe a CP-server? I think I will stick to the server I'm on now, though)) and the game now costs 10 euros, but in the Beta, it will be 20 euros, so decide fast

.
And one last tip: if you want to go exploring a cave and don't want any unpleasant surprises, be sure to go to options and set the difficulty to 'peaceful'. This will stop the monsters from spawning. However, I don't know if this is the case for the monster-spawners too...
Anyway, GL!