pretty good
the best of this type of game made in flash, good work, except i found a very easy way to win(works in all modes):
click over to the stonemason tab and wait
when the troll reaches 100% click on it
when the arrows reach 100% use them in the center of a group of enemy units
click on the zeppelin when it reaches 100%
wait (which means do not spend any money and do not use the troll) until the lightning reaches 97% or so (ignore the alarm that starts sounding, you'll kill them before they kill you) then click on the catapult in the stonemason tab as many times as you can then quickly click on the lightning then the troll and watch the enemy's health plummet woohoo
its nice you thought of an original way to lose life, but having an actual base that loses life when attacked makes much more sense and works better, just my opinion though