This is hilarious and I love it.
But. It REALLY needs a way to zoom out on some of the later levels. The enemy can remember where everything is in relation to other things; players probably can't.
If you ace any level from 15-20 on easy, it immediately bumps you into "normal," with no way to go back to the easy levels and try again for the accomplishments.
This is not a good feature.
Could benefit from separate commands for raise and lower (e.g. shift+click always equals lower). A lot of times it'll raise when it want it to lower, or lower when I want it to raise.
Clicking on "achievements" under "reset" resets the achievements even if you don't click "OK" afterward.
The helicopter pilot isn't always too smart about targeting: if there's a UFO it'll shoot it down, even if there's a huge cluster of machete throwers, demons, and whatsits throwing their heads at the house, doing much more damage than the UFO is.
I have a bugged saved game on the last level which always freezes at :45 till the next zombie wave. Kind of disappointing since I'd just finished saving everybody on the island and was going to blow up the bridge next.
I keep running into this bug where a sniper tower has both ammo and people in it but doesn't fire on approaching zombies even though I haven't told it to hold fire. Very annoying, since it means all attempts to clear more area fail.
Game has a memory leak. Memory requirement for Flash container plugin goes up and up the longer I play, eventually getting to over 1GB (just for this game!) and then freezing up.
Are you putting customers and/or purchases into an array and not punching them out of the array once the music is sold and/or the customer leaves? Just a guess.