The game is programmed well enough and everything seems to do what it's supposed to. It could have used more variation in level design, more traps, and so forth. The concept is good and can be pretty fun, though I think something similar has been done before with stationary objects rather than a physics-based one. ("Mario & Wario" comes to mind.) It's not a bad idea, but it was poorly executed.
Of the 12 levels, I only had problems with the last. Levels 1 through 11 do a decent job of teaching you the physics of the game, but there's really no tenseness to the levels, wherein Bob is in direct danger of being killed. It's just all busy-work and timing with a whole lot of "red herring" dangers.
The game is also challenging... but it's a completely artificial difficulty. Due to how the "grab" engine was coded, when the left mouse button is held down, there's an invisible sphere of influence which pulls the box toward the mouse cursor. If you move the cursor too fast, the box leaves the sphere of influence and thus, leaves your control. The box also seems to have some collision detection issues with the walls.
The sound effects are fine, but that music is one of the more annoying things I have ever heard in ANY game. I'm VERY glad there's a mute button.
All and all, this isn't the worst thing I've ever played on Newgrounds, but it's nothing to write home about, either.