Good game. I think you should add another way for the difficulty to increase over time, because 25 minutes into the tutorial level I was still going.
I think a simple solution would be to make the black spiny guy appear more and more sparsely as time goes on. The issue is that as the block dropping speeds up, the interval of black spiny guys stays the same. Therefore the more the game tries to challenge you, the more you get a free way out.
Also sorry if I sound overly negative, I would like to add that this is one of the more entertaining yet simplest games I’ve played!