Nice twist on platformers! I also like the simple but strong art style.
There was a lot times when I wanted the game to go a bit faster. The character controlled well but the gaps between gameplay were very long, like the camera panning back to the start, waiting for the block to come down the tube, and even at the end of a level there's a small delay before the "next level" button is shown.
I really liked the last level, I saw the new block and put the first one in the crevice to see what happened... only to recognise it the second time I had it. I thought "what if it's like that other game" and sure enough it was :D and then there was a puzzle using it immediately. It was a really strong way of ending the game.