Thanks for the replies guys!
Yeah, I noticed the sound bug, but I couldn't solve because I'm away from my PC. The problem is I assigned a channel to the steps, and the other files are played automatically. So something must be going wrong with this.
About the screensize, this was part of the experience. I'd like the game to have a small play area + big mouse grabbing bag.
The dragging needs to be improved: The "sine behavior" you mentioned happens because it's setting the force according to the distance with your mouse, but it doesn't reach it so it keeps adding forces and the object keeps orbiting around it
About the levels: I want to make a larger level instead of several small ones. This was supposed to be a arcade game where you play in order to improve your high score. But I'm also considering adding levels and some background story.