Some really good ideas here. The pixel art looks great, including the backgrounds. The tutorial is really clear and helpful. The GUI accurately shows the wizard's weight at any given time--an excellent touch.
Unfortunately, I had a lot of difficulty with the controls. In particular, dealing with enemies was very difficult. Switching from low weight (to jump) to high weight (to crush an enemy) is a really clever idea, but in practice it felt awkward; I'm not sure if it's because I had to control the wizard's weight with my left hand (which I associate with movement). Some experimentation might help to find a more natural control scheme.
Some music and more sound effects would also have great.