There will be a way to turn it off at some point soon.  The people who make videos have requested this several times.

Minecraft has a selection cube too but it's black.  In Mythruna a black cube could almost never be seen so I made it more visible and when you are building it is useful.

At some point there will be a distinction between building and just "gaming" in the UI... at that point the selection cube will only be there in build mode.  Even before that, I will add a way to toggle it on and off... I just have to get some other things done first that are driving me crazy.

I see, thanks a lot, that will be awesome!

I think it would be a very good idea to get rid of the selection cube. It totally destroys immersion to have this thing crop up everywhere you move your mouse. Just do it like minecraft does with the crosshair or similar. Other than that it's a great game and it's nice to have a world with ready made buildings etc to start off in. The cube really does spoil everything for me though. You have such nice water with animation and sound so you really feel you are going for a swim ... apart from the big yellow cube. I hope you understand what I mean and that I am not trying to criticise for the sake of it but rather to improve one aspect of the game. Thanks for listening!