It is just an auto-tiling system. You place blocks, they automatically connect to each other. :) WASD to move in the editor. 1 - Ground 2 - Stone Click to place/delete blocks. R to reset stage. Oh... and you might be able to play the level you created somehow... Who knows? Maybe [SPACE]?
I might make a game based on this engine. I might release the full engine with in-depth tutorial to make it possible for everyone to use.