Thank you Devin! Actually the reason I began to consider improving performance was an email I received from a guy who said the game froze and caused animation problems on Galaxy S2 quite often. I did quite a research about performance and code optimization. Turned out my code was fairly inefficient!

I have applied the lessons I've learned, in the version you have, and the version that I will publish this weekend. And the guy actually didn't send an email back (as we agreed). So I assume this has been a successful move.
By the way, what's the highest level you have reached? I just want to know how urgent is it to make all 60 levels. the game has now 43.