Nice idea, but I agree with the others about the controls. Not much about the use of the mouse, that might work using perhaps a touch device, but because the balloon doesn't respond well. It takes a lot of gas to go up and drop down to fast, sometimes moves very fast on one side, other times you can make it move a few pixels to land on the tank to pick up.
Touching the wall drop you down fast, other times made me bunch a lot left and right between two walls.
If you polish the game you can make it interesting. It reminded me H.E.R.O. that I was playing when I was young, and I got frustrated in the same way for the difficulty to control it.
Again, fix it and it will become an interesting game to try :-)
Link to H.E.R.O. in case you don't know the game:
https://en.wikipedia.org/wiki/H.E.R.O._(video_game)