I really like this prototype and I think it is very unique. At least I have never seen this concept before.
I am aware that this is a prototype at a very early stage - I think it has a lot of potential for additional extension. You could start the game out with fewer directions (2 instead of 4) or the number of segments a piece consists of, just to name a few ideas.
One thing I noticed while playing was that by intuition I did not expect the arrow keys to move the blocks right away. Instead I was expecting the arrow keys to only set the direction and afterwards requiring a confirmation (for instance the Space key) to be moved eventually. I was hit by surprise a few times when the arrow key immediately moved my piece. But this might just be me...
Generally, great concept!