Well..
I played through the game. And I did enjoy it, but I also do have some thoughts, comments, and suggestions.
1. First, I think I should point out that the mute in the menu doesn't work when I hover over it I get the message "THE GAME IS CURRENTLY muted2 WOULD YOU LIKE TO UNMUTE?" (yes the 2 is there, and it is all in caps) when the game is in fact not muted and there are no other options to mute it.
2. For the first part of the game the upgrades to the penguin types are pretty balanced, the last level set and the last penguin type are not. The last level set "metal" can be beaten with full zombie penguins and a couple of specials. The last penguin type "robot" is so insanely expensive (87,000/unit for full final upgrade total 435,000, 475,000 if you count the extra penguin and I do) compared to the max level money (my max earned was ~17000 on level 30, my average on high payout levels 31-40 was around 13,000) , that it would take forever to turn your squad into them. A few things that may help balance this:
a. Add some harder enemies in level set 4, you already have it themed, play with it some. Or....
b. Put more enemies on level set 4 levels.
c. Add higher payout for enemies in level set 4. Or...
d. Add upgrades for the egg collector (higher attraction/area of effect, multiplier values, etc).
3. I agree with what some others have said, hotkeys would really be nice for the specials. After purchasing the bomb I found myself rarely using it unless I was trying to just barely win a level. I probably would have used it more if it had a hotkey. I also agree that an indicator for area of effect would be nice. Especially as the levels expand.
4. The end was a bit of an anticlimax considering the game did have a bit of a story, it leaves it with an unfinished feeling.
5. When you go back through levels it would be nice if the game would not bring you back to the end. So then if you are collecting money for instance in relaxing level 30, you don't have to keep flipping back through the pages.
6. I don't expect great pathfinding from a flash game, but in all fairness to some previous comments the penguin pathfinding does kind of suck. I had more than one level that I lost simply because my penguins got stuck.
I also wonder why the zombie penguins are a step up in speed, though I suppose that is really neither here nor there. Overall I did enjoy playing it, I just can't see myself re-playing it, or going through the trouble of maxing out the stats. I can tell you put a great deal of work into this, but it does feel unfinished and have some minor bugs. U really enjoyed the concept. If you do make a sequel (and I hope you do) I would suggest adding some more plot development an actual ending and a revamped upgrade system/level balance. I think this is a well earned 4/5 and 9/10. Keep up the good work.