Another Box2D physics game? There are a lot of those coming out recently.
These games all have 1 fatal flaw, same as yours. The physics is too good. Sometimes, we don't want perfect physics, because it can make the game very hard and frustrating to play. Slightest little bump and the thing falls over. Picking up and dropping objects becomes too hard because the slightest little tip and the tower falls over.
Now this is what 'makes the challenge' but because of how Box2D does it, it can be far too sensitive and difficult for the game. I mean here, it's just another physics stacking game, I've seen heaps of them lately. But it's so sensitive and difficult to line up with the fact that the center or rotation is where you click, that it becomes nearly impossible not to tip the tower. At least in the other games it doesn't have that, so it's more about your building skills. In this game it's just about how well you can click the exact center and cross your fingers that the blocks angular momentum doesn't drop the whole thing.
And frankly, I'm getting bored with this latest 'tower building' game craze. It doesn't show competence as a game developer, since all the work is being done by Box2D, that someone else coded. And it isn't original. And most of the time, it isn't even fun.
This is more or less a rant against all these 'tower building' games, so don't take it too personally.