I really enjoy this concept. I feel like more feedback regarding the weight mechanic would make this game a bit more enjoyable. I found myself not being heavy enough to crush enemies at times and it was quite hard to predict a jump arc that would get me to the next platform without hitting the spikes. I think a simple animation when your falling and at an appropriate weight to crush things would add some nice feedback to the player. I really like the idea of being able to change your jump arc by altering your weight, it can be pretty hard to get right without some visual feedback. All in all you've done a very good job.