Both times I've gotten to level 50, the program crashed and I had to close out. Overall, entertaining game, but too difficult. Just reducing the rate that the upgrades to the city get more expensive will go a long way to correcting it in my opinion.
Well, I won, but was largely unsatisfied. At least until I saw the comment on how this was a test. You should have that as the ending script, and it would have been worth it.