Great job. I really like the concept and aesthetics of this game.  I like the mechanic of not just being able to move objects around to solve puzzles but also being able to change their size. The physics worked well and great choice of music. I played it on an older machine (without a dedicated graphics card) and the WebGL performed well. I use Chrome and the controls worked fine. 

Some suggestions and ideas (which you may already have on your improvements list): 

• Not sure why the energy/power meter doesn't start at 100%, but if it did, the loss of power on every discharge would be more noticeable. Maybe you could move the meter onto the gun itself.
• What should happen when all the power is used up? I had to restart the game manually to complete the first level after using up all the power.
• For added difficulty maybe you could limit the range of the gun so you have to be within a certain distance of an object for it to have an effect.  
• I like the particle effect when firing the gun, but a lazer/electrical/lightening bolt that goes from the gun to the object would be cool.
• Auto save after completing every level so I can resume from where I left off when returning to the game.

Overall I enjoyed the game and the concept.