I guess you think that all blocky games are like Minecraft, right? That is about as true as the statement that all RTS games are like Command & Conquer. I hope you will revise your opinion once you have the opportunity to play the game. :)
I suggest you make a demo in that case, cause at this point it is unclear what you are selling if it isn't a minecraft look alike. :)
Yes, you are right. I plan to release a demo version when the alpha is released.
