Since a few days (I believe, since an update a week or so ago) 3 out of 10 ball throws attempts fail miserably. That is to say, the screen doesn't respond.
I'd give the previous version [of the Can Knockdown 2] 4 or 5 stars, this one I'll have to rate at 2, I regret to admit!
I wrote the review above a fortnight ago. I'll have to reiterate: this game is remarkably unresponsive, running on a brand new iPhone 4S. Does the developer expect it to run on anything older? If so, very gullible of him to believe that.