The actions required to proceed in this game make absolutely no sense at all. Oh, I need starfishes to put in the reef. Naturally, all sea creatures give you starfishes when you in return give them a pearl. Things like that just are not intuitive AT ALL.
Good start. You should probably not make it so the first round starts when you place your first tower. Just let the player hit the "Next Wave" button when he's ready to start.
This game would be a 5/5 instead of a 1/5 if you just didn't have all the requirements of spending real money to accomplish anything of value. Sure, having premium stuff for money content is acceptable, but you have the basics requiring it.
Oh ok, I get it. The guy is lying to you. That really doesn't help people get started on your game. I just about closed it right away when I was given the wrong directions.
I still don't understand how after 4 games now you haven't figured out that being able to click on the minimap to scroll to that location should be added. Fun game just baffled that you've left that out.
The targeting system needs work. We should be able to set targeting to first, last, strongest, weakest, etc to make best use of the special abilities of our units.
 "Fish Castle Escape")
 "The idiot test")
 "Mini Castle Defense")
 "Heir")
 "Sorcery Quest")
 "Clown’s Revenge")
 "Depict1")
 "DS test")
 "Epic War 4")
 "MARDEK RPG: Chapter 3")
 "Protector IV")
 "Mario Cross")
 "preload test")
 "The Adventures of Salt and Pep")
 "YGOp: Yugioh Parody"){kind=logo}
 "RSp: Runescape Parody")
 "Defend Sealand"){kind=icon}
 "Bubble Sea")