It's a really cool project and performs reasonably well but I have issues with some of the interface choices:<p>1. The navigation controls are non-intuitive and don't follow most 3D movement conventions. I wanted right-click panning and some shortcut for orbiting (not having to change modes).<p>2. Positioning is erratic. When building something it would randomly refuse to let me draw on top of some cubes even when I precisely positioned my cursor on the top cube surface. Positioning guides would be nice: Highlight adjacent surfaces, draw alignment axis, etc.<p>3. Conversely, erasing a bunch of blocks would fail because the erase cursor would "hop" on top of (some not all) blocks I wanted to erase.<p>4. The "thicken" operation sounds handy but never worked for me even once I figured out (I think) that you have to select blocks first. I expected I could select blocks and then pull them up or out to duplicate them.<p>5. Having a multiuser environment default to fill/drawing mode is a horrible idea since _everyone_ spews blocks all over the landscape destroying stuff before getting the hang of it. Suggestion: Give everyone a protected 30x30x30 home sandbox where no one else can draw. Everywhere else would be free range.<p>Overall, you have the tech down but the UI needs playtesting. Watch novices and Minecraft-ers try doing something more than scribble with it. You'll know your interface is working when you start seeing more than blobs and piles littering your world.