I expected improvements in the sequel
First of all, i'd like to point out that this game is almost identical to Canyon Defense, which is pretty good.
I'll help you out, just in case you decie to brave a third (it can be the same as the second, with the following improvements):
-More money
-Less expensive upgrades please
-Flying enemies go across horizontally
-A little more advance warning of what's coming next, and with details like HP. The number of enemies doesn't really mean much.
and that's about it. A good try.