The majority of the development on the game previously was the CPU (he literally developed a virtual CPU) and the engine. He's not using a pre-made engine, I remember reading about the physics issues he was having with movement a while back.C'mon, Rydian - this game has been in development for quite some time now. Even if the engine looks "fine for a pre-alpha", it falls short of expectations, not to mention that the art design so far, the very thing this trailer was supposed to show, as I previously stated, looks boring and poopie. I won't get into the "Notch" discussion since I think he's a bit of a narcissistic douche, but what I'm going to say is that so far, I'm not really interested in the game outside of the "16-bit computer you can program for!" factor.
You can feel free to go develop your own virtual CPU and 3D game engine and then come back and tell me how quickly it went...