I like this game so much, but sometimes the jump does not register correctly, meaning falling down some platforms and do some areas more time than necessery. The other thing that bugs me it's that I can't absorb blocks while jumping: If I can place them mid-air, why can't I remove them as well? Plus I can't re-unlock the speedrun mode in the demo, even after taking all the stars.
But, like I said, I like this game anyway.