This was cool. I like the idea driving it.
I think it's a bit difficult, though. Tried a few times and didn't get even close to completing my stack haha.
I would prefer smooth movement to the block-by-block approach. I feel like the game is based on doing something speedily and the bit-by-bit movement hinders that objective. Also, a bit of music would have been nice.
That being said, I can see this becoming a cool game. Smooth the movement, lower the difficulty curve, polish the art, maybe add some form of progression to keep it interesting. I'd play that!
Nice work :)